Every season of The Big Bang Theory ever, ranked from best to worst by thousands of votes from fans of the show. The best seasons of The Big Bang Theory!

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.

Pilot

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.

The Big Bran Hypothesis

Leonard asks a woman out after he finds out that Penny is seeing someone.

The Fuzzy Boots Corollary

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.

The Luminous Fish Effect

Fearing he's wasting his time on Penny, Leonard ends up making a connection with Leslie.

The Hamburger Postulate

Penny hosts a Halloween party, putting Leonard, Sheldon, Wolowitz, and Koothrappali through a new test of their social skills.

The Middle-Earth Paradigm

With Wolowitz AWOL with one of her friends, Penny's recruited to fill in for him on the guys' Halo team

The Dumpling Paradox

Raj's parents set him up on a blind date, but just when he discovers he can talk to her, she shows interest in Sheldon.

The Grasshopper Experiment

When they're invited to present at a physics conference, Sheldon's reluctance to share the credit leads to a tiff between him and Leonard, and Penny's intervention only exacerbates the situation.

The Cooper-Hofstadter Polarization

Leonard and Sheldon each lie to avoid seeing Penny's concert, but Sheldon's is a bit too complicated for his own good.

The Loobenfeld Decay

With his friends knowing how sour he acts when sick—and avoiding him as a result—Sheldon is nursed by Penny, who hasn't a clue what she's in for.

The Pancake Batter Anomaly

With Sheldon rattled over meeting Dennis, a 15-year-old physicist who's smarter than he, Leonard helps him look for a way to debunk Dennis's research.

The Jerusalem Duality

Sheldon finds himself booted from the gang's Physics Bowl team and replaced with Leslie, so he forms his own team, hoping to prove he's superior.

The Bat Jar Conjecture

When delivery of another collectible leads to Penny's lashing out at Leonard, he decides it's time to give up his habit, much to his friends' protestation.

The Nerdvana Annihilation

The rest of the gang fall for Sheldon's twin sister, and Leonard's plan to win her heart is derailed when Sheldon declares he'll be the one to decide who can date her.

The Pork Chop Indeterminacy

Penny wants to throw a surprise party for Leonard, but Sheldon's indulgence at an electronics store throws her off-track.

The Peanut Reaction

Penny's break-up spurs Leonard to summon the courage to ask her out, and each goes to Sheldon for advice on their upcoming date.

The Tangerine Factor

Penny's first date with Leonard goes awry; Penny finds Sheldon to be an unwilling confidant.

The Bad Fish Paradigm

A jealous Leonard reacts to Penny's new guy by rebounding with Leslie.

The Codpiece Topology

Sheldon creates a monster when he introduces Penny to online gaming.

The Barbarian Sublimation

Raj gets an inflated ego and makes a play for Penny after being referenced in a magazine article.

The Griffin Equivalency

Leonard and his friends stage an intervention to force Sheldon to face his fear of driving.

The Euclid Alternative

Sheldon and the gang are confused when a young grad student is attracted to him.

The Cooper-Nowitzki Theorem

When Sheldon bans Penny from the apartment for numerous minor infractions, she decides to retaliate.

The Panty Piñata Polarization

Leonard inadvertently steals away the new woman Wolowitz thinks is the love of his life.

The Lizard-Spock Expansion

Sheldon is thrilled when Leonard starts dating a woman who meets Sheldon's stringent standards.

The White Asparagus Triangulation

Leonard asks Penny for advice when his new relationship starts moving too fast.

The Vartabedian Conundrum

Penny starts dating Leonard's handsome colleague; Leonard and his friends are tortured by Sheldon's obsession with gift-giving etiquette.

The Bath Item Gift Hypothesis

Penny's criticism of Wolowitz's romantic life pushes him into depression and AWOL for a fighting robot battle the rest of guys are depending on him for.

The Killer Robot Instability

Sheldon creates a scientific procedure for making friends.

The Friendship Algorithm

Sheldon's solution to Penny's financial difficulty leads to a confrontation between Leonard and Penny's ex-boyfriend.

The Financial Permeability

Leonard and Penny are drawn together after a disastrous visit from Leonard's mother.

The Maternal Capacitance

A paintball game leads to a fight between Sheldon and Penny, and romance for Leslie and Wolowitz.

The Cushion Saturation

Leonard, Sheldon and Wolowitz are ecstatic to learn that a famous science-fiction actress (Summer Glau) is on board the train they are taking to San Francisco.

The Terminator Decoupling

Penny's home business turns into a complete nightmare when Sheldon takes over.

The Work Song Nanocluster

Penny squares off with a new beautiful female neighbor who may become the building's "new Penny."

The Dead Hooker Juxtaposition

A fellow comic book enthusiast's hitting on Penny leads to Leonard and Howard going to a bar's Ladies' Night.

The Hofstadter Isotope

Leonard and Koothrappali escort a heartbroken Wolowitz to Las Vegas, and Sheldon becomes locked out of his apartment and must stay with Penny.

The Vegas Renormalization

Penny's second date with Stuart sees her making a comment that gives Leonard new hope for a relationship with her. Wolowitz realizes there's a crucial error in a NASA project he's working on.

The Classified Materials Turbulence

The guys' plan to work over the summer at the North Pole makes Penny revaluate her feelings for Leonard.

The Monopolar Expedition

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.

The Electric Can Opener Fluctuation

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.

The Jiminy Conjecture

Howard and Raj visit a Goth nightclub to pick up women while Sheldon attempts to build a better Penny using chocolate-based behavior modification.

The Gothowitz Deviation

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.

The Pirate Solution

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.

The Creepy Candy Coating Corollary

Sheldon becomes Leonard's teacher in order to understand football, while an incident with flying a kite threatens Howard and Raj's friendship.

The Cornhusker Vortex

A squabble between Leonard and Penny sees Sheldon playing mediator, though out of his own incovenience from the sitiation rather than altruism.

The Guitarist Amplification

With Leonard, Howard and Raj away camping in the desert, an injured Penny has only Sheldon to rely on.

The Adhesive Duck Deficiency

After he's humiliated on National Public Radio, Sheldon vows to destroy Kripke, while Wolowitz tries not to destroy his new relationship with Bernadette.

The Vengeance Formulation

Penny gets help from Sheldon in order to understand what Leonard's work is, while Wolowitz develops a jealousy when Leonard starts hanging out with his new girlfriend.

The Gorilla Experiment

A Christmas visit from his mother has Leonard discovering she's kept a lot of news from him that she shares with Sheldon and worrying if she'll approve of his romance with Penny.

The Maternal Congruence

Leonard is aghast to find out a secret of Penny's: she believes in psychics. Meanwhile, Sheldon tries to assist Koothrappali in picking up a girl at a university mixer.

The Psychic Vortex

When their apartment is robbed, Leonard and Sheldon turn to their friends to create a state-of-the-art security system.

The Bozeman Reaction

Sheldon's search for the answer to a physics problem leads him to work at the Cheesecake Factory with Penny.

The Einstein Approximation

Leonard can only bring one guest on a trip to see CERN's Large Hadron Collider (the world's largest and highest energy particle accelerator) in Switzerland on Valentine's Day.

The Large Hadron Collision

Sheldon winds up in traffic court when he gets a ticket because of Penny.

The Excelsior Acquisition

When the guys find a ring from "The Lord of the Rings" at a garage sale, it threatens to tear them apart.

The Precious Fragmentation

Sheldon's friends come to his aid when his fear of public speaking stands between him and a coveted award.

The Pants Alternative

A fight between Leonard and Penny threatens their relationship, while Sheldon battles Wil Wheaton in bowling.

The Wheaton Recurrence

When Leonard and Penny aren't speaking, Sheldon goes to extremes to keep them both happy.

The Spaghetti Catalyst

Leonard and Sheldon compete for the attention of a famous female physicist.

The Plimpton Stimulation

Leonard tells Penny about how he met Sheldon for the first time...and what happened to the elevator.

The Staircase Implementation

While Penny worries that dating Leonard has ruined her for normal guys, Wolowitz and Koothrappali search for Sheldon's perfect match online.

The Lunar Excitation

Penny tags along on Sheldon's first ever date; Wolowitz finds a new use for a robotic arm.

The Robotic Manipulation

Realizing he will not live long enough to download his consciousness into a robot body, Sheldon tries to extend his life span.

The Cruciferous Vegetable Amplification

The guys are concerned as Sheldon searches for an alternative to human companionship.

The Zazzy Substitution

An embarrassing secret of Wolowitz's comes to light, while Sheldon and Raj have a small war at work.

The Hot Troll Deviation

Leonard realizes he’s the only one without a girlfriend, while Sheldon wants to get rid of his.

The Desperation Emanation

Leonard keeps an affair a secret from Sheldon, Howard and Raj.

The Irish Pub Formulation

Sheldon's answers during an FBI interview put Wolowitz's security clearance in jeopardy.

The Apology Insufficiency

While the guys camp in line for a long-awaited movie screening, Penny and Bernadette invite Amy to her first slumber party.

The 21-Second Excitation

Penny asks Leonard to lie to her father, while Howard, Raj and Bernadette pull an all-nighter at a telescope.

The Boyfriend Complexity

Amy finds she has sexual feelings for Penny's ex, while Koothrappali and Wolowitz try to prove who would be the better superhero.

The Alien Parasite Hypothesis

The guys find a "super" use for Penny's new boyfriend, Zack, when they enter a costume contest as the Justice League.

The Justice League Recombination

Leonard's idea for a smartphone app derails his friendship with Sheldon.

The Bus Pants Utilization

Bernadette runs into her ex-boyfriend while attending a science event with Wolowitz.

The Love Car Displacement

Hoping it will make him a better teacher, Sheldon has Penny give him acting lessons. Raj has fantasies about a friend's girlfriend.

The Thespian Catalyst

A wealthy donor to the university makes Leonard consider how far he's willing to go for the sake of science.

The Benefactor Factor

As Wolowitz contemplates taking things with Bernadette to the next level, Leonard rekindles his relationship with Raj's sister.

The Cohabitation Formulation

Sheldon becomes concerned when everybody begins to hang out at Raj's apartment and discovers Leonard is the center of the group.

The Toast Derivation

Sheldon is baffled by Wolowitz's magic trick. Meanwhile, Leonard realizes dating Priya may make it impossible to continue being friends with Penny.

The Prestidigitation Approximation

Sheldon's online-game account is hacked by Todd Zarnecki, who then proceeds to steal all his items prompting the guys to go on a quest to retrieve them.  Penny, Bernadette and Amy discuss how Penny groomed Leonard to be willing to try various things and more adventurous boyfriend... for some other woman — Priya.

The Zarnecki Incursion

Sheldon and Amy decide to start several rumors about the others as a test. Meanwhile, Howard takes his relationship with Bernadette to even higher level.

The Herb Garden Germination

When Leonard spends too much time in the shower with Priya, Sheldon charges Leonard with two violations of the roommate agreement. However, before he can get too far, Priya uses her skills as a lawyer to nullify the charges due to the agreement's vague wording, much to Sheldon's dismay. When the guys take advantage of Priya's skills in order to eat Greek food on pizza night, Sheldon goes to Penny, who invites him to a girls' night out with Amy and Bernadette, which Sheldon agrees to after Penny mentions that they may be talking trash about Priya. After the girls drink some cocktails, they decide to take Sheldon dancing, which Sheldon reluctantly goes along with. After dancing, Sheldon takes an intoxicated Amy back to her apartment and as well as talking about Priya, meets a monkey who is addicted to smoking cigarettes. Amy tells Sheldon not to give in to Priya's law skills, before kissing him and going to her bathroom to vomit.

The Agreement Dissection

Raj attempts to cure his social anxiety disorder while Penny uses Bernadette to spy on Leonard and his girlfriend.

The Wildebeest Implementation

When Howard finally breaks the news to his mom that he's engaged to Bernadette, it lands her in the hospital.

The Engagement Reaction

When Bernadette receives her PhD, Wolowitz feels emasculated. Raj and Leonard swap places and Penny does something she's regrets.

The Roommate Transmogrification

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.

The Skank Reflex Analysis

A fight between Sheldon and Penny leaves Amy caught in the middle, while Leonard tries to spice up his long-distance relationship with Priya.

The Infestation Hypothesis

Leonard and Amy get to know each other better, while Howard and Bernadette spend the weekend with Mrs. Wolowitz.

The Pulled Groin Extrapolation

Penny plays Matchmaker for Raj, which results in him finding a girl he is comfortable talking to.

The Wiggly Finger Catalyst

Sheldon and Leonard get invited to a party at Wil Wheaton's house, and Howard gets an out-of-this-world opportunity.

The Russian Rocket Reaction

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.

The Rhinitis Revelation

A cute comic book artist puts Leonard and Priya’s relationship to the test, while Sheldon tries to scare the guys for Halloween.

The Good Guy Fluctuation

Amy becomes heartbroken when she discovers that Penny and Bernadette went wedding dress shopping without her.

The Isolation Permutation

Leonard and Penny try hanging out as friends on a 'non-date', but end up purposely ruining each others chances with perspective dates. Meanwhile, Sheldon enlists the help of Bernadette and Amy to overcome his fear of birds.

The Ornithophobia Diffusion

When Stuart asks Amy out on a date, Sheldon must confront his feelings and consider where his relationship with Amy is going.

The Flaming Spittoon Acquisition

Leonard must face his fears after being contacted by his high school tormentor.

The Speckerman Recurrence

Sheldon gets in trouble with Amy when he isn't impressed by her recent accomplishment, and Howard must come to grips with Bernadette's dislike of children.

The Shiny Trinket Maneuver

Leonard, who broke up with Priya, asks Penny out to a spur-of the-moment romantic dinner for two, and the duo contemplates on their relationship.

The Best Seasons of The Big Bang Theory

The Best Seasons of The Big Bang Theory

Season 3

Season 1

Season 4

Season 6

Season 5

Season 9

Season 2

Season 7

Season 12

Season 8

Season 10

Season 11