A comic strip, created by Hal Foster in 1937 and distributed by King Features. As far as I can tell, it's always been a Sunday-only strip, which surely makes it easier to tell stories than in those itty-bitty daily strips. It also doesn't use word balloons -- all text, including dialogue, is placed in captions.
Val started the strip as a youngster living in Britain, where his father, the deposed king of Thule, lived in exile. Most of his childhood was skipped over to get to the prince's adventures as an adult, when he met and befriended King Arthur, Sir Gawain, Sir Lancelot, and the rest of the Knights of the Round Table. Between slaying dragons and rescuing maidens, he also acquired the fabulous Singing Sword, was knighted by King Arthur, and got his father reinstated as Thule's king -- all in the first four years of the strip's existence!
Val married Queen Aleta of the Misty Isles in 1946, but she was quickly kidnapped. While pursuing her, Val ended up in North America, about a thousand years before Christopher Columbus! They lived in North America for a while, and their first son, Arn, was born there a year or so later. Over the years, Val's family has grown to include four more kids and a grandchild.
Foster and "Prince Valiant" received the Reuben Award from the National Cartoonists' Society in 1957. The strip was turned into a movie, with Robert Wagner as the star, in 1954, and the series was briefly turned into a comic book that same year. An animated series called "The Legend of Prince Valiant" ran on the Family Channel in 1991; Robby Benson provided the voice of Val, while Tim Curry was Sir Gawain. There was also a live-action film released in England in 1997.
Foster retired from drawing the strip in 1971 and stopped writing it in 1980. He died in 1986. The current strip is drawn by John Cullen Murphy and written by a variety of different writers.
Addendum: Habakkuk notes: "You forgot to mention that he, Mr. Spock from Star Trek and Moe from the Three Stooges all share the same barber."
Research from http://www.toonopedia.com/val.htm