Kristoffer Polaha (born February 18, 1977) is an American actor. He is best known for his starring roles on television as Jason Matthews in North Shore, Nathaniel "Baze" Bazile in Life Unexpected, and Henry Butler in Ringer. He has also appeared in films Devil's Knot (2013), Wonder Woman 1984 (2020) and Jurassic World Dominion (2022).

Since 2016, Polaha has appeared in numerous Hallmark movies and a seven-part series of Hallmark Movies & Mysteries films titled Mystery 101, saying "as an actor, I am leaning into Hallmark because it's fun to sit with my seven-year-old and show him what I do for a living. These are family-friendly movies. I'm leaning in because my 91-year-old Nana finally thinks I've made it in Hollywood because I'm on Hallmark."

Polaha was born in Reno, Nevada to Esther and Jerome Polaha. Polaha's family has Czech roots. His father was a Washoe District Court Judge. Polaha is the youngest of four brothers. He left Reno in the early 1990s to attend Robert Louis Stevenson boarding school in Pebble Beach, California. In 1999, he graduated from New York University Tisch School of the Arts, where he earned a Bachelor's degree in Arts. He moved to Los Angeles on July 4, 2001.

Early in his career, Polaha appeared in theatre productions, including Ragtime Revue at Lincoln Center, The Long Days Journey Into Night at the Roundabout Theater, Bread & Butter at Provincetown Playhouse, and Uncle Vanya at the Stella Adler Conservatory. In early 2000s, Polaha began appearing in small roles in several American television series and films. His first on-screen appearance was a role as Gavin in the episode "Plus One" of comedy-drama series That's Life. He had roles in television series Angel, Roswell, Birds of Prey, Tru Calling, House, CSI: Miami, It's Always Sunny in Philadelphia, Bones and Close to Home. Polaha gained attention by portraying John F. Kennedy Jr. in the TBS film America's Prince: The John F. Kennedy Jr. Story (2003) opposite Portia de Rossi. In 2021, Polaha told Highbrow Magazine: "That was the biggest TV movie that TBS had ever released. I think 40 million people watched it that night, and I had a picture in Times Square of my face."

In 2004, he won the lead role of Jason Matthews on the prime-time soap opera North Shore. The series centered on the staff and guests of the fictional Grand Waimea Hotel and Resort. North Shore concluded in January 2005 after a 21-episode, single-season run. Polaha and his family lived in Hawaii for a year and their son was born there. In 2007, Polaha took the role of Carlton Hanson on drama television series Mad Men. In 2008, Polaha starred on the series Miss Guided and appeared in the biographical film Billy: The Early Years (2008). In 2009, he appeared in several guest starring television roles, including The Ex List, Dollhouse, Without a Trace and Better Off Ted. In 2010, he began portraying Nate Bazile, a bar owner who discovers he has a teenage daughter Lux Cassidy (Britt Robertson), on the teen drama series Life Unexpected. The series garnered mostly positive feedback during its two seasons, with many reviews favorably comparing the show to the critically acclaimed series Gilmore Girls and Everwood. In November 2010, Polaha signed a talent holding deal with CBS. Polaha founded a production company titled Podunk Productions in 2010. He played writer Henry Butler in The CW's thriller crime series Ringer until the series conclusion in 2012. Las Vegas Weekly gave Ringer a mixed review, saying it was "a little silly but also juicy and well-acted". In 2012, he landed a guest role on the second season of MTV's teen comedy series Awkward.

Polaha starred as John Galt in Atlas Shrugged: Part III, which was released on September 12, 2014. He appeared in the movies Devil's Knot (2013), Back in the Day (2014), Where Hope Grows (2015) and Aberrant (original name: Vineland) (2016). Where Hope Grows centers on the friendship between Calvin (portrayed by Polaha), a former professional baseball player and Produce (David DeSanctis), a young man with Down syndrome. The film grossed $1.2 million at the box office. He had a lead role as Jodie King in the short film Frontman (2016). He earned a Jury Award for Best Actor at Seattle Shorts Film Festival for his performance in Frontman. In 2017, Polaha played Jeffrey in five episodes of the comedy-drama television series Get Shorty.

Polaha has starred in several original Hallmark Channel films, including Dater's Handbook (2016) opposite Meghan Markle, Rocky Mountain Christmas (2017) opposite Lindy Booth and Pearl in Paradise (2018) alongside Jill Wagner. Especially Rocky Mountain Christmas was a success for the network. Polaha commented the film's popularity by saying: "Rocky Mountain Christmas won the night on cable. We had the highest ratings, not just the highest ratings ever in the history of Hallmark Movies & Mysteries, but we won the night across all the cable channels. It was a big deal for Hallmark, and it was a big deal for us as a cast because it really did set our movie apart. It was definitely one of those special moments." In 2018, he appeared in six episodes of the thriller television series Condor and starred in two films, Beneath the Leaves and Bachelor Lions.

He played detective Travis Burke in Hallmark's mystery television film series Mystery 101 (2019) opposite Jill Wagner. The film series included seven movies and the first one aired on January 27, 2019. Polaha portrayed Michael Truett in the Christian drama film Run the Race (2019), released on February 22, 2019 by Roadside Attractions. The film made $2.3 million in its opening weekend, finishing 10th at the box office. In November 2018, Polaha revealed that he will appear in Wonder Woman 1984 (2020), directed by Patty Jenkins; he played the 'host' to the resurrected spirit of Chris Pine's character. On July 26, 2019, The Hollywood Reporter announced that Polaha will appear in Hallmark Channel's Christmas-themed television film Double Holiday (2019) opposite Carly Pope. In 2020, he had a small role as Courthouse Reporter 2 in Hulu's drama miniseries Little Fires Everywhere starring Reese Witherspoon and Kerry Washington. Polaha starred in Hallmark's original Christmas film A Dickens of a Holiday! (2021) as Jake Dorsey, famous action star who grew up in Dickens, Ohio.