Ritter was born on February 17, 1980, in Los Angeles, California, to actors Nancy Morgan and John Ritter.^[1] He is a grandson of actors Tex Ritter, who died six years before Ritter was born, and Dorothy Fay. His stepmother is actress Amy Yasbeck. Ritter has three siblings, including actor Tyler Ritter.^[2]

Ritter's television debut happened during the opening credits of the sixth season for his father's sitcom Three's Company. Actress Joyce DeWitt recalls: "Our director, Dave Powers, was just shooting from the cuff when we would go on location to shoot the credits. There was a rough draft, but not really a game plan. And because we were going to be all day on location (at the Los Angeles Zoo in Griffith Park), people brought their children, their wives, whatever, it was kind of a group event, and Davey was just grabbing anybody and everyone to throw into those credits. In my credit, where I'm down and this little boy toddles in, that's Jason Ritter, John's first child."^[3][4][5]

He attended middle and high school at the Crossroads School in Santa Monica, California, alongside Simon Helberg, who became his roommate at NYU.^[6] Ritter attended and graduated from New York University's Tisch School of the Arts, where he studied at the Atlantic Theater Company. He later studied at the Royal Academy of Dramatic Art in London.^[7]

Ritter made his professional acting debut at age 10, playing Harry Neal Baum in the 1990 television film The Dreamer of Oz: The L. Frank Baum Story. Several years later, he had a supporting role as Martin Brockett in the 1999 film Mumford, a dramedy directed by Lawrence Kasdan.

Ritter's film work throughout the early 2000s included prominent parts in teen-oriented projects such as Swimfan (2002), Freddy vs. Jason (2003), and Raise Your Voice (2004). Between 2003 and 2005, he appeared as Kevin Girardi, the disabled brother of the titular main character, on the CBS family drama series Joan of Arcadia. Next, he played a young man struggling to come terms with his sexuality in the dark comedy Happy Endings (2005), with Stephen Hunter of The Washington Post commenting, "The acting in this ensemble is of such a high order that the movie simply takes you in and makes you feel these lives as real."^[8]

Ritter's portrayal of an Ivy League college student in The Education of Charlie Banks (2007) was met with critical acclaim: The Hollywood Reporter referred to it as a "head-turner" performance that combined "a believably brooding intensity with a bad boy swagger that brings to mind [a] young Matt Dillon."^[9]

Following a supporting role in the satirical 2008 comedy The Deal, Ritter appeared briefly as Jeb Bush in the biographical drama W, directed by Oliver Stone. On preparing for the role, he said, "I watched everything that I possibly could and read some books about [the] Bush family [and] Jeb."^[10] That same year, he produced and starred in the independent dramedy Good Dick with his girlfriend at the time, Marianna Palka, making her directorial debut.^[11] A look at the relationship between an introverted girl (Palka) and the video store assistant (Ritter) vying for her attention, the film drew a mixed reception,^[12] but Empire's Anna Smith was enthusiastic in her appraisal: "Ritter's character — a romantic reformed druggie — is one to root for, and [the film] entertains enough to get by, marking Palka and Ritter as talents to watch."^[13]

In 2010, Ritter began playing the recurring role of Mark Cyr on NBC's Parenthood. The performance earned him a nomination for the 2012 Primetime Emmy Award for Outstanding Guest Actor in a Drama Series.^[14] His next project was the 2011 independent comedy A Bag of Hammers, where he starred as a felon who winds up taking care of a neglected child; in a mixed review, The Hollywood Reporter felt that its tone was "muddled" but believed it "starts off strong, offering funny, well timed dialogue between Sandvig [and] Ritter."^[15] Also that year, he co-starred in The Perfect Family, with Kathleen Turner and Emily Deschanel, which critic Frank Scheck felt worked solely on the strength of its performances: "Turner is deeply sympathetic as the religious matriarch [...] while Ritter and Deschanel are thoroughly believable as the grown children who love their mother despite her oft-expressed disapproval of their actions."^[16]

Between 2012 and 2016, Ritter starred in the voice role of Dipper Pines on the Disney Channel animated series Gravity Falls, a show about a pair of twins deciphering the weird goings-on in the mysterious titular town. The series was universally praised,^[17] with Alasdair Wilkins of The A.V. Club calling it "funny, emotional, beautiful, and terrifying in equal measure."^[18] Ritter had prominent parts in five independent features between 2012 and 2013: The End of Love, Free Samples, I Am I,^[19] The Big Ask, and The East. It was announced in February 2013 that he would star as Gavin in Us & Them, a sitcom pilot based on the British television comedy Gavin & Stacey.^[20] While subsequently picked up as a series by Fox, Us & Them was cancelled before it could premiere,^[21] with the show's seven episodes eventually being released by Crackle.^[22]

Ritter's appearance in Wild Canaries (2014), a throwback to classic whodunits, was met with praise: Justin Chang of Variety called the film "eventful, plot-driven [and] fun," adding that "[Kevin] Corrigan and especially Ritter are solid in their hefty supporting roles."^[23] He headlined the independent drama About Alex that same year, playing a young man who finds solace in a group of old friends after attempting to take his own life. In his review for RogerEbert.com, Brian Tallerico said, "What's kind of refreshing about About Alex is that the predictable map through the clichés of this subgenre that seems to be charted in the opening scenes isn't quite followed," adding "Ritter finds [the] emotional undercurrent that's often missing from these troubled characters. There's something honest in the way his voice quivers that makes his depression seem more genuine."^[24]

Ritter had a supporting role as the main character's movie star ex-boyfriend in the 2015 comedy-drama The Meddler, and began playing Lord Frederick Bellacourt—an illiterate twin—that same year on the acclaimed historical sitcom Another Period,^[25] a parody of Downton Abbey.^[26] In their review of Period, which ran for three seasons on Comedy Central,^[27] The A.V. Club felt that Ritter brought "an earnestness" to the wacky material.^[28] Next, he starred as a man suffering from retrograde amnesia in the post-apocalyptic drama Embers (2015); Sight and Sound critic Anton Bitel called it "a reflection of the human condition as philosophically compelling as it is emotionally intelligent," adding "No film has either moved or provoked me as much this year."^[29] In 2016, Ritter co-starred in the well-reviewed ensemble comedy The Intervention and received positive notices for his role in Carrie Pilby, an adaptation of the novel of the same name.^[30][31][32]

In the satirical dark comedy Bitch (2017), Ritter re-teamed with director Marianna Palka to play Bill, a promiscuous husband whose wife suddenly takes on the mannerisms of a wild dog. Writing for IndieWire, Erick Kohn said, "The usually sweet-natured Ritter boldly plays against type [as] an American Psycho-like creep," adding that "[the film] works best when it focuses on Bill's ongoing shock at the sudden demand for his responsibility, as he fights through the task of delivering his kids to school and suddenly loses traction in the workplace. A fierce portrait of unwieldy comeuppance, it's both hilarious and terrifying to watch Bill take in the strange events around him."^[33]

Ritter's portrayal of Kevin Finn—a depressed financial worker tasked with preventing humanity from self-destruction—in Kevin (Probably) Saves the World was warmly received by critics.^[34][35] The show ran for a single season on ABC between October 2017 and March 2018.^[36] Next, he appeared in The Tale (2018), a drama based on the childhood sexual abuse suffered by Jennifer Fox—the film's writer and director—at the hands of her running coach. Ritter played perpetrator William "Bill" Allens, earning strong reviews for his performance: "Ritter has never been better" said Matt Goldberg of Collider,^[37] while The Atlantic's David Sims commented, "Handed the tough roles of mentors who shift into monsters, Ritter and [Elizabeth] Debicki subtly calibrate their performances as necessary, projecting a protective edge in one moment and a predatory one in the next. Their transformations are extraordinary to watch, and necessary to reckon with."^[38] Ritter said the experience of making the film had been a challenging one, and that there were times after a day's shooting when he "had to go home and let it all out."^[39]

In 2019, Ritter played the voice role of Ryder—a member of the Northuldra tribe—in Walt Disney's Frozen 2, which broke box office records upon its release.^[40] He began starring as biotech engineer Pat Rollins on the critically acclaimed superhero series Raising Dion the same year,^[41] with Aaron Pruner of Thrillist commenting that Ritter's involvement "adds the nuanced character work he's known for."^[42] The show ran for two seasons on Netflix before being cancelled in April 2022.^[43]

In a casting choice that drew attention for being "meta,"^[44] Ritter appeared as Deputy Denny Reese in two episodes of the true crime Hulu miniseries Candy (2022), where the character—along with his colleague, played by Justin Timberlake—investigates the 1980 murder of Texan housewife Betty Gore. Gore was portrayed by Ritter's wife, Melanie Lynskey, while the perpetrator—Candy Montgomery—was played by Timberlake's wife, Jessica Biel. The following year, Ritter voiced principal character Jonathan Fall in the animated series Captain Fall, a dark comedy that ran for one season on Netflix.^[45]

It was announced in March 2023 that Ritter had been cast in the CBS reboot of Matlock,^[46] which began airing in October 2024.^[47] In his review of the first season, IndieWire's Ben Travers found Ritter to be one of the show's biggest assets, writing, "[he] has long deserved a regular showcase like [this]."^[48]

From October 1999 to 2013, Ritter was in a relationship with Marianna Palka. They met while they were both studying at the Atlantic Theater Company in New York City.^[49] In 2017, Ritter became engaged to New Zealand actress Melanie Lynskey after four years of dating.^[50] The couple had their first child, a daughter, in December 2018.^[51] They wed in 2020.^[52]

Speaking in 2010 about the death of his father, Ritter said, "I think it helped me realize how fragile we all are. At the end of the day, you can be a health freak or a body builder, but a truck might hit you. Or you might be a huge, larger than life personality and it could all be taken away in the next second. I learned to tell people in my life how I feel about them a little bit more."^[53]

Ritter has been open about his struggle with alcoholism, and how his relationship with Lynskey gave him the strength to get sober: "I thought she would be incredible for someone who deserved her, basically," he said in 2023. "And I didn't feel like I was that person.... It was only after [a] year into not drinking where I started to go, 'Oh, maybe I can promise some things to someone else. Maybe I can be this person.'"^[54]