The Big Bang Theory
The Big Bang Theory is centered on five characters living in Pasadena, California: roommates Leonard Hofstadter and Sheldon Cooper; Penny, a waitress and aspiring actress who lives across the hall; and Leonard and Sheldon's equally geeky and socially awkward friends and co-workers, mechanical engineer Howard Wolowitz and astrophysicist Raj Koothrappali. The geekiness and intellect of the four guys is contrasted for comic effect with Penny's social skills and common sense.
Where to Watch The Big Bang Theory
Where to stream every episode from all 12 seasons of The Big Bang Theory. Filter these episodes by what's available to watch free or on your streaming services using the tabs above.
Season 1Rent or Buy
S01 E01Sep 25, 2007
Pilot Sep 25, 2007 Brilliant physicist roommates Leonard and Sheldon meet their new neighbor Penny, who begins showing them that as much as they know about science, they know little about actual living.
S01 E02Oct 2, 2007
The Big Bran Hypothesis Oct 2, 2007 Leonard volunteers to sign for a package in an attempt to make a good impression on Penny, but when he enlists Sheldon for help, his attempt at chivalry goes terribly awry.
S01 E03Oct 9, 2007
The Fuzzy Boots Corollary Oct 9, 2007 Leonard asks a woman out after he finds out that Penny is seeing someone.
S01 E04Oct 16, 2007
The Luminous Fish Effect Oct 16, 2007 Sheldon's getting fired forces him to explore what life has to offer outside physics, leaving Leonard to take drastic action to snap his friend out of his funk.
S01 E05Oct 23, 2007
The Hamburger Postulate Oct 23, 2007 Fearing he's wasting his time on Penny, Leonard ends up making a connection with Leslie.
S01 E06Oct 30, 2007
The Middle-Earth Paradigm Oct 30, 2007 Penny hosts a Halloween party, putting Leonard, Sheldon, Wolowitz, and Koothrappali through a new test of their social skills.
Season 2Rent or Buy
S02 E01Sep 23, 2008
The Bad Fish Paradigm Sep 23, 2008 Penny's first date with Leonard goes awry; Penny finds Sheldon to be an unwilling confidant.
S02 E02Sep 30, 2008
The Codpiece Topology Sep 30, 2008 A jealous Leonard reacts to Penny's new guy by rebounding with Leslie.
S02 E03Oct 7, 2008
The Barbarian Sublimation Oct 7, 2008 Sheldon creates a monster when he introduces Penny to online gaming.
S02 E04Oct 14, 2008
The Griffin Equivalency Oct 14, 2008 Raj gets an inflated ego and makes a play for Penny after being referenced in a magazine article.
S02 E05Oct 21, 2008
The Euclid Alternative Oct 21, 2008 Leonard and his friends stage an intervention to force Sheldon to face his fear of driving.
S02 E06Nov 4, 2008
The Cooper-Nowitzki Theorem Nov 4, 2008 Sheldon and the gang are confused when a young grad student is attracted to him.
Season 3Rent or Buy
S03 E01Sep 22, 2009
The Electric Can Opener Fluctuation Sep 22, 2009 When Sheldon learns the guys tampered with his expedition data he got from the arctic, he leaves to Texas in disgrace. This results in the guys following him, which threatens Leonard's hope for some romantic time with Penny and the guys' friendship with Sheldon.
S03 E02Sep 29, 2009
The Jiminy Conjecture Sep 29, 2009 Leonard and Penny struggle to recover from an awkward first hookup while Sheldon and Howard stake their best comic books on a bet to determine the species of a cricket.
S03 E03Oct 6, 2009
The Gothowitz Deviation Oct 6, 2009 Howard and Raj visit a Goth nightclub to pick up women while Sheldon attempts to build a better Penny using chocolate-based behavior modification.
S03 E04Oct 13, 2009
The Pirate Solution Oct 13, 2009 Raj must find a new job or be sent back to India, but Sheldon has a solution, which leaves Leonard and Penny dealing with Howard as a third wheel.
S03 E05Oct 20, 2009
The Creepy Candy Coating Corollary Oct 20, 2009 After overhearing that Wil Wheaton is entering a trading-card competition, Sheldon decides to enter it himself. Meanwhile, Penny sets up one of her friends on a date with Wolowitz.
S03 E06Nov 3, 2009
The Cornhusker Vortex Nov 3, 2009 Sheldon becomes Leonard's teacher in order to understand football, while an incident with flying a kite threatens Howard and Raj's friendship.
Season 4Rent or Buy
S04 E01Sep 24, 2010
The Robotic Manipulation Sep 24, 2010 Penny tags along on Sheldon's first ever date; Wolowitz finds a new use for a robotic arm.
S04 E02Oct 1, 2010
The Cruciferous Vegetable Amplification Oct 1, 2010 Realizing he will not live long enough to download his consciousness into a robot body, Sheldon tries to extend his life span.
S04 E03Oct 8, 2010
The Zazzy Substitution Oct 8, 2010 The guys are concerned as Sheldon searches for an alternative to human companionship.
S04 E04Oct 15, 2010
The Hot Troll Deviation Oct 15, 2010 An embarrassing secret of Wolowitz's comes to light, while Sheldon and Raj have a small war at work.
S04 E05Oct 22, 2010
The Desperation Emanation Oct 22, 2010 Leonard realizes he’s the only one without a girlfriend, while Sheldon wants to get rid of his.
S04 E06Oct 29, 2010
The Irish Pub Formulation Oct 29, 2010 Leonard keeps an affair a secret from Sheldon, Howard and Raj.
Season 5Rent or Buy
S05 E01Sep 23, 2011
The Skank Reflex Analysis Sep 23, 2011 Penny is worried with how damaged her friendship with the guys will be in the aftermath of her sleeping with Raj while Sheldon becomes the leader of the paintball team.
S05 E02Sep 23, 2011
The Infestation Hypothesis Sep 23, 2011 A fight between Sheldon and Penny leaves Amy caught in the middle, while Leonard tries to spice up his long-distance relationship with Priya.
S05 E03Sep 30, 2011
The Pulled Groin Extrapolation Sep 30, 2011 Leonard and Amy get to know each other better, while Howard and Bernadette spend the weekend with Mrs. Wolowitz.
S05 E04Oct 7, 2011
The Wiggly Finger Catalyst Oct 7, 2011 Penny plays Matchmaker for Raj, which results in him finding a girl he is comfortable talking to.
S05 E05Oct 14, 2011
The Russian Rocket Reaction Oct 14, 2011 Sheldon and Leonard get invited to a party at Wil Wheaton's house, and Howard gets an out-of-this-world opportunity.
S05 E06Oct 21, 2011
The Rhinitis Revelation Oct 21, 2011 Sheldon's mother, Mary Cooper, comes to visit, but Sheldon is annoyed that she also spends time with the rest of the gang, instead of catering to his every demand.
Season 6Rent or Buy
S06 E01Sep 28, 2012
The Date Night Variable Sep 28, 2012 With his friends on dates, Raj must face his loneliness. Also, Wolowitz is caught in an argument between Bernadette and his mom, even while he’s in space
S06 E02Oct 5, 2012
The Decoupling Fluctuation Oct 5, 2012 When Sheldon learns that Penny is thinking about breaking up with Leonard, he tries to intervene. Meanwhile, in space, the other astronauts pick on Howard.
S06 E03Oct 12, 2012
The Higgs Boson Observation Oct 12, 2012 Amy feels threatened when Sheldon hires a young female assistant, and the pressure of being in space takes its toll on Wolowitz.
S06 E04Oct 19, 2012
The Re-Entry Minimization Oct 19, 2012 When Wolowitz returns from space, he doesn’t get the hero’s welcome he expected. Meanwhile, Game Night turns into a battle of the sexes.
S06 E05Oct 26, 2012
The Holographic Excitation Oct 26, 2012 The gang celebrates Halloween at Stuart’s comic book store. Meanwhile, Leonard seduces Penny with science.
S06 E06Nov 2, 2012
The Extract Obliteration Nov 2, 2012 Sheldon’s relationship with Stephen Hawking is threatened over a game of “Words with Friends,” and Penny secretly enrolls in a class at the local college.
Season 7Rent or Buy
S07 E01Sep 27, 2013
The Hofstadter Insufficiency Sep 27, 2013 With Leonard away, Sheldon and Penny spend quality time together sharing intimate secrets. Also, Wolowitz helps Raj get over his ex-girlfriend.
S07 E02Sep 27, 2013
The Deception Verification Sep 27, 2013 Leonard and Sheldon's friendship is tested; Wolowitz's relationship with his mom causes a threat to his masculinity.
S07 E03Oct 4, 2013
The Scavenger Vortex Oct 4, 2013 When the entire gang competes in a scavenger hunt designed by Raj, it brings out the best - and worst - in everyone.
S07 E04Oct 11, 2013
The Raiders Minimization Oct 11, 2013 Beverly Hofstadter writes a psychology book about Leonard which Penny buys and reads. Sheldon wants to ruin something for Amy after she ruins an Indiana Jones movie for him. Raj and Stuart try online dating.
S07 E05Oct 18, 2013
The Workplace Proximity Oct 18, 2013 Amy starts working at Caltech which causes friction with Sheldon. Howard agrees with Sheldon who mentions this to Bernadette causing a big fight for the Wolowitzes.
S07 E06Oct 25, 2013
The Romance Resonance Oct 25, 2013 Sheldon's latest scientific breakthrough leaves him feeling like a fraud; a romantic gesture between Howard and Bernadette causes Penny to up her game with Leonard.
Season 8TBS | Rent or Buy
S08 E01Sep 23, 2014
The Locomotion Interruption Sep 23, 2014 Leonard and Amy make an unexpected trip to Arizona to fetch Sheldon; Penny interviews for a job at Bernadette's company; Stuart's relationship with Mrs. Wolowitz disturbs Howard.
S08 E02Sep 23, 2014
The Junior Professor Solution Sep 23, 2014 When Sheldon must teach a class, Howard decides to take it. Amy takes advantage of the tension between Penny and Bernadette.
S08 E03Sep 30, 2014
The First Pitch Insufficiency Sep 30, 2014 Wolowitz feels nervous when he is asked to throw the first pitch at a Los Angeles Angels game. Penny and Leonard want to prove Sheldon wrong after he says he and Amy are the better couple.
S08 E04Oct 7, 2014
The Hook-Up Reverberation Oct 7, 2014 Raj's honesty comes back to haunt him when his new girlfriend is unfriendly to Penny. The guys think about becoming part owners in Stuart's store.
S08 E05Oct 14, 2014
The Focus Attenuation Oct 14, 2014 During their weekend in Las Vegas, Bernadette and Amy accuse Penny of being a buzz kill. The guys try to invent the next big thing.
S08 E06Oct 21, 2014
The Expedition Approximation Oct 21, 2014 Sheldon and Raj test whether they could survive a dark-matter research expedition in a salt mine by simulating the conditions in a steam tunnel deep underground. Leonard and Penny seek advice from Howard and Bernadette after they fight about money.
S08 E07Oct 31, 2014
The Misinterpretation Agitation Oct 31, 2014 The guys try to help Penny out of an awkward work dilemma, when a smitten doctor shows up at her door after her flirtatious sales techniques work a little too well. Meanwhile, Amy and Bernadette argue over whether or not female scientists should play up their sexuality.
Season 9Rent or Buy
S09 E01Sep 22, 2015
The Matrimonial Momentum Sep 22, 2015 After driving to Vegas to get married, Penny struggles with Leonard’s confession that he kissed another girl. Also, Sheldon doesn't know how to act after Amy pushes pause on their relationship.
S09 E02Sep 29, 2015
The Separation Oscillation Sep 29, 2015 Leonard confronts the woman he kissed on the North Sea in an attempt to set Penny's mind at ease. Also, Sheldon films a special episode of "Fun with Flags" after his breakup with Amy, and Bernadette feels guilty about withholding a secret from Penny.
S09 E03Oct 6, 2015
The Bachelor Party Corrosion Oct 6, 2015 The guys' science skills are put to the test when they get a flat tire during Leonard's bachelor party weekend in Mexico. Also, the girls force Penny to finally tell her family that she eloped with Leonard.
S09 E04Oct 13, 2015
The 2003 Approximation Oct 13, 2015 Sheldon learns of an impending change in his living arrangements and decides to revert back to 2003, a simpler time before he met Leonard and Penny. Also, Howard and Raj form a band to play at the Comic Book Store.
S09 E05Oct 20, 2015
The Perspiration Implementation Oct 20, 2015 The guys take a fencing lesson from Barry Kripke and Sheldon finds himself in an awkward position when Kripke expresses interest in Amy. Also, when Stuart struggles to get female customers at the Comic Book Store, Penny, Amy and Bernadette come by to help him out.
S09 E06Oct 27, 2015
The Helium Insufficiency Oct 27, 2015 In the midst of a nation-wide helium shortage, Sheldon and Leonard take desperate measures to get the supplies they need. Also, Penny and Bernadette download a dating app on Amy's phone to try and find her a new man.
Season 10Rent or Buy
S10 E01Sep 20, 2016
The Conjugal Conjecture Sep 20, 2016 After Sheldon’s mother and Leonard's father share an evening together, everyone deals with an awkward morning the next day. Also, Penny’s family arrives for the wedding ceremony, including her anxiety-ridden mother, Susan, and her drug dealing brother, Randall.
S10 E02Sep 27, 2016
The Military Miniaturization Sep 27, 2016 Colonel Williams, an Air Force representative from the Department of Material Command sits down to talk with Wolowitz.
S10 E03Oct 4, 2016
The Dependence Transcendence Oct 4, 2016 Tensions rise when the boys struggle to complete their government project on time and Sheldon tries an energy drink to stay awake. Also, Penny and Amy go to a “party” at Bert the geologist’s house, and Koothrappali learns Bernadette’s true feelings about her pregnancy when they clean out the future baby room.
S10 E04Oct 11, 2016
The Cohabitation Experimentation Oct 11, 2016 When Amy’s apartment floods, she proposes a “cohabitation experiment” with Sheldon. Also, Howard and Bernadette are upset when Koothrappali learns the gender of the baby before they do.
S10 E05Oct 18, 2016
The Hot Tub Contamination Oct 18, 2016 Leonard and Penny must separate a quarreling Sheldon and Amy when their cohabitation does not go as planned, and Sheldon threatens to break off their relationship when Amy refuses to adhere to the bathroom schedule. Also, Howard and Bernadette find unexpected guests at their house when they decide to stay home from a planned vacation.
S10 E06Oct 28, 2016
The Fetal Kick Catalyst Oct 28, 2016 Penny is surprised to learn she has fans of her performance in "Serial Ape-ist" when she attends Van Nuys Comic Con with Leonard. Also, Amy hosts a Sheldon-style brunch at Penny’s apartment, and Wolowitz makes an impulsive purchase when he starts stressing out about the baby on the way.
S10 E07Nov 4, 2016
The Veracity Elasticity Nov 4, 2016 In order to continue living with Sheldon, Amy lies to him about repairs being made to her apartment and they host an "on location" episode of "Fun With Flags" in Penny’s apartment. Also, Leonard lets Penny decorate Sheldon’s old room after he learns that she has been secretly moving Leonard’s collectibles into storage.
Season 11Rent or Buy
S11 E01Sep 26, 2017
The Proposal Proposal Sep 26, 2017 In the eleventh season opener, Amy gives Sheldon an answer to his proposal while Howard and Bernadette struggle with some unexpected news.
S11 E02Oct 3, 2017
The Retraction Reaction Oct 3, 2017 Leonard angers the university – and the entire physics community – after he gives an embarrassing interview. Also, Amy and Bernadette bond over having to hide their success from Sheldon and Howard.
S11 E03Oct 10, 2017
The Relaxation Integration Oct 10, 2017 Sheldon struggles with picking a wedding date. Amy decides she wants a wedding near a cliff which Sheldon doesn't want. Meanwhile Raj and Stuart fight over one of Bernadette's co-workers.
S11 E04Oct 17, 2017
The Explosion Implosion Oct 17, 2017 As Howard worries about fatherhood, he and Sheldon bond when they jointly assemble a model rocket. Meanwhile, Penny bonds with Leonard's mother, Beverly, much to his concern.
S11 E05Oct 24, 2017
The Collaboration Contamination Oct 24, 2017 Sheldon and Koothrappali confide in Bernadette when they can't handle Amy and Wolowitz working together. Also, Penny and Leonard learn new tactics for how to deal Sheldon from an unlikely source.
S11 E06Nov 3, 2017
The Proton Regeneration Nov 3, 2017 Sheldon goes head-to-head with Wil Wheaton for the role of the new Professor Proton. Also, Penny steps in to take care of Halley when Bernadette and Wolowitz both wind up on bed rest.
Season 12CBS All Access | Rent or Buy
S12 E01Sep 25, 2018
The Conjugal Conjecture Sep 25, 2018 Sheldon and Amy's honeymoon runs aground in New York, while Penny and Leonard discover they are uncomfortably similar to Amy's parents, Mr. and Mrs. Fowler. Also, Koothrappali insults physicist Neil deGrasse Tyson and starts a Twitter war.
S12 E02Sep 28, 2018
The Wedding Gift Wormhole Sep 28, 2018 Sheldon and Amy drive themselves crazy trying to figure out what "perfect gift" Leonard and Penny gave them for their wedding. Also, Koothrappali decides he wants to settle down and asks his father to arrange a marriage for him.
S12 E03Oct 5, 2018
The Procreation Calculation Oct 5, 2018 The Wolowitzes' life gets complicated when Stuart starts bringing his new girlfriend home. Also, Penny and Leonard talk about starting a family while Koothrappali explores an arranged marriage.
S12 E04Oct 12, 2018
The Tam Turbulence Oct 12, 2018 When Sheldon won't tell anyone why he's never mentioned Tam, his childhood best friend, Leonard takes matters into his own hands. Also, Bernadette and Penny take out Raj’s fiancée, Anu, for dinner to get the skinny on her.
S12 E05Oct 19, 2018
The Planetarium Collision Oct 19, 2018 When Amy doesn’t have time to work on super-asymmetry, Sheldon goes to great lengths to ensure she’s available to work with him even it if means accidentally sabotaging her career in the process. Also, Koothrappali doesn’t want Wolowitz to join him in hosting a show at the planetarium.