Bernard "Barney" Fife is a fictional character in the American television program The Andy Griffith Show, portrayed by comic actor Don Knotts. Barney Fife is a deputy sheriff in the slow-paced, sleepy, southern community of Mayberry, North Carolina. He appeared in the first five seasons (1960–65) as a main character, and after leaving the show towards the end of season five, made a few guest appearances in the three color seasons (1965–68). He also appeared in the first episode of the spin-off series Mayberry R.F.D. (1968–1971), and in the 1986 reunion television film Return to Mayberry. Additionally, Barney appeared in the Joey Bishop Show episode "Joey's Hideaway Cabin", and unnamed in the first episode of The New Andy Griffith Show.

In 1999, TV Guide ranked Barney Fife ninth on its 50 Greatest TV Characters of All Time list.

According to Andy Griffith, the character of Barney Fife was suggested by Don Knotts himself. At the same time The Steve Allen Show was ending, Knotts was looking for work. When he saw the episode of The Danny Thomas Show featuring Andy Taylor, he called Griffith suggesting that his sheriff character might reasonably need a deputy. Griffith liked the idea and suggested that he call Executive Producer Sheldon Leonard. Griffith later recalled that Don Knotts' contribution was the show's saving grace because he was uncomfortable with the original concept to have Andy Taylor being the comic lead. In an interview with The Archive of American Television, Griffith admitted, "The second episode was called 'Manhunt' and I knew by that episode that Don should be the comic and I should play straight for him. That made all the difference."

Fife appeared on The Andy Griffith Show from the show's beginning in 1960 until 1965, when Knotts left the show to pursue a career in feature films. It is explained that Fife had left Mayberry to take a job as a detective in Raleigh, North Carolina. In reality, Knotts left because Griffith said he would end the show after 5 seasons, only for Griffith to change his mind, but Knotts decided to honor his commitment and left the series, thinking he would not get another chance to make movies. Knotts reprised the character in guest appearances each season until The Andy Griffith Show left the air in 1968. Barney also appeared in the inaugural Mayberry R.F.D. episode, in which Andy and Helen Crump marry. In 1971, the character, whose name is not explicitly mentioned, appears in the premiere episode of The New Andy Griffith Show, visiting the mid-sized city of Greenwood to catch up with Mayor Andy Sawyer, who looks exactly like Andy Taylor and shares some of Taylor's earlier mannerisms and friendships with Fife, Goober Pyle, and Emmett Clark. Fifteen years passed before the character was again reprised in the reunion film Return to Mayberry in 1986. By then, Fife had moved back and become the town's acting sheriff.

Barney Fife is outwardly smug and self-important, covering up his insecurities and low self-confidence with a display of bravado. He presents himself as an expert on such diverse subjects as firearms, martial arts, women, singing, wilderness survival, psychology, and American history. He frequently tries to impress others with his knowledge or skill in areas where his expertise is quite limited. He wishes to be perceived as "a man of the world", but he is quite naïve, and his fear of appearing ignorant leaves him easily duped. This gullibility is evident when, for example, he is tricked into buying a lemon from a crafty old widow  Although he believes himself a skilled singer, he has a tin ear although at other times, when he is not trying to show off, he has a pleasant singing voice, performing duets with Andy and his guitar. His attempts to impress others sometimes cause him to accidentally reveal both personal and police secrets, often with dire consequences. Barney can be emotional, and he often overreacts to challenging situations with panic, despair, or bug-eyed fear.

As a law enforcement officer, Barney is overly officious and insistent on doing things "by the book" to the point of absurdity. In one case when Andy was briefly summoned away, as acting sheriff, Barney proceeded to book and lock up everyone in town for various minor infractions ("Andy Saves Barney's Morale"). In at least one case, though, he is commended for his apparent overzealousness, after he tickets the state governor's car for being parked illegally. Barney tends to be alarmist and overreacts to potential dangers. In a case where he believed an ex-convict was coming back to Mayberry to attack Sheriff Taylor, he deputized Goober Pyle and Otis Campbell (who are even more inept) and attempted to provide 24-hour protection for the sheriff, although in fact no threat existed and the bodyguards did little except interfere with each other.

Barney is often frustrated with the primitive technological tools available to the Mayberry sheriff's department. He sometimes attempts to modernize the department by acquiring equipment of little use in sleepy Mayberry, such as an intercom system for the jailhouse and a search-and-rescue dog. On occasion, Barney believes his experience as a long-time deputy qualifies him to be a sheriff. In a second-season episode, he is offered the position of sheriff in the nearby town of Greendale, only to learn from Andy the difference between serving as sheriff versus deputy. He runs against Andy, only to later withdraw. In Return to Mayberry, Barney finally holds the position of "acting sheriff" of Mayberry and runs for the office proper, but at the end, encourages the town to vote for Andy, who has returned to Mayberry.

One frequent source of comedy is Barney's incompetence with firearms. After numerous negligent discharges (usually with a Smith & Wesson or Colt .38 caliber revolver), Andy restricts Barney to carrying his gun unloaded, with only one bullet in his shirt pocket, "in case of an emergency". However, Barney tends to load his gun unnecessarily, and often ends up firing it into the floor, the ceiling, or his own gun holster. The negligent discharge of Barney's gun becomes a running gag, usually followed by Barney sheepishly handing his gun to Andy. Another recurring gag has Barney locking himself or both Andy and himself in one of the jail cells, with the keys just out of reach. Another running gag is Barney being captured by escaped criminals twice. A third gag is that even when Barney is competent, the result backfires on him. In one episode, Barney drives a motorcycle/sidecar quite well on patrol, but Mayberry is so small a town that the motorcycle is practically useless for local law enforcement.