James Aurness was born in Minneapolis, Minnesota on May 26, 1923; he dropped the “u” in his last name when he started acting. His parents were Rolf Cirkler Aurness (a businessman) and Ruth Duesler (a journalist). His father’s ancestry was Norwegian; his mother’s was German. The family name had been Aurness, but when Rolf’s father, Peter Aurness, emigrated from Norway in 1887, he changed it to Arness. Arness and his family were Methodists. Arness’ younger brother was actor Peter Graves. Peter used the stage name “Graves”, a maternal family name.

Arness attended John Burroughs Grade School, Washburn High School, and West High School in Minneapolis. During this time, Arness worked as a courier for a jewelry wholesaler, loading and unloading railway boxcars at the Burlington freight yards in Minneapolis, and logging in Pierce, Idaho. Despite “being a poor student and skipping many classes”, he graduated from high school in June 1942.

Although Arness wanted to be a naval fighter pilot, he was concerned his poor eyesight would bar him. However, his 6-ft, 7-in (2.01 m) frame ended his chances because the limit for aviators was set at 6 ft, 2 in (1.88 m). He was drafted into the US Army and reported to Fort Snelling, Minnesota, in March 1943. As a rifleman, he landed on Anzio Beachhead on January 22, 1944, with the 2nd Platoon, E Company, 2nd Battalion, 7th Infantry Regiment of the 3rd Infantry Division. Arness – due to his height – was the first man to be ordered off his landing craft to determine the depth of the water; it came up to his waist. He was severely wounded in his right leg during the Battle of Anzio, and medically evacuated from Italy to the U.S., where he was sent to the 91st General Hospital in Clinton, Iowa. His brother, Peter, (later known as actor Peter Graves), came to see him when he was back in the U.S., beginning his long recuperation, assuring him to not worry about his injuries, that likely he could find work in the field of radio. After undergoing several surgeries, he was honorably discharged from the Army on January 29, 1945. His wounds continued to trouble him, though, throughout the remainder of his life. In his later years, he suffered with chronic leg pain that often became acute, and was sometimes initiated when he was mounted on horses during his performances on Gunsmoke. His military decorations included the Bronze Star, the Purple Heart, the European-African-Middle Eastern Campaign Medal with three bronze battle stars, the World War II Victory Medal, and the Combat Infantryman Badge.

After his discharge from the service, Arness entered Beloit College in Wisconsin. He began his entertainment career as a radio announcer at Minneapolis station WLOL in 1945.

Arness married Virginia Chapman in 1948, and adopted her son Craig (1946 – December 14, 2004). Besides Craig, Arness and Chapman also had a son, Rolf, (born February 18, 1952) and a daughter, Jenny Lee Arness (May 23, 1950 – May 12, 1975). Rolf Aurness became World Surfing Champion in 1970. Craig Arness founded the stock photography agency Westlight and also was a photographer for National Geographic. When they divorced in 1963, Arness was granted legal custody of the children. Daughter Jenny died of a drug overdose in 1975. Former wife Virginia died of a drug overdose in 1977.

An urban legend has it that John Wayne was offered the leading role of Matt Dillon in the longtime favorite television show Gunsmoke, but he turned it down, instead recommending James Arness for the role. The only true part of this story is that Wayne did indeed recommend Arness for the part. Wayne introduced Arness in a prologue to the first episode of Gunsmoke, in 1955. The Norwegian-German Arness had to dye his naturally blond hair darker for the role. Gunsmoke made Arness and his co-stars, Milburn Stone, Amanda Blake, Dennis Weaver, Ken Curtis, Burt Reynolds, and Buck Taylor, world-famous, and ran for two decades, becoming the longest-running primetime drama series in US television history by the end of its run in 1975. The series’ season record was tied in 2010 with the final season of Law & Order and tied again in 2018 with season 20 of Law & Order: SVU. Unlike the latter show, Gunsmoke featured its lead character in each of its 20 seasons; Gunsmoke also aired 179 more episodes, and was in the top 10 in the ratings for 11 more seasons, for a total of 13, including four consecutive seasons at number one.

In 1978, Arness married Janet Surtees. She survived him.

For his contributions to the television industry, Arness has a star on the Hollywood Walk of Fame at 1751 Vine Street. In 1981, he was inducted into the Western Performers Hall of Fame at the National Cowboy & Western Heritage Museum in Oklahoma City. Arness was inducted into the Santa Clarita Walk of Western Stars in 2006, and gave a related TV interview.

Though identified with Westerns, Arness also appeared in two science-fiction films, The Thing from Another World (in which he portrayed the title character) and Them!. He was a close friend of John Wayne and co-starred with him in Big Jim McLain, Hondo, Island in the Sky, and The Sea Chase, and starred in Gun the Man Down for Wayne’s company. He also starred in a 1988 TV remake of Wayne’s 1948 classic Red River.

On the 50th anniversary of television in 1989 in the United States, People magazine chose the top 25 television stars of all time. Arness was number six.

In 1996, TV Guide ranked him number 20 on its 50 Greatest TV Stars of All Time list.

James Arness: An Autobiography was released in September 2001, with a foreword by Burt Reynolds (who had been a cast member of Gunsmoke for several years in the 1960s). Arness noted that he realized, “[I]f I was going to write a book about my life, I better do it now … ’cause I’m not getting any younger.”

Arness died of natural causes at the age of 88 years at his Brentwood home in Los Angeles on June 3, 2011. His body was interred in the Sanctuary of Abiding Hope alcove in the Jasmine Terrace section of the Great Mausoleum at Forest Lawn Memorial Park in Glendale, California.