Ka-Bar (trademarked as KA-BAR) is the contemporary popular name for the combat knife first adopted by the United States Marine Corps in November 1942 as the 1219C2 combat knife (later designated the USMC Mark 2 combat knife or Knife, Fighting Utility), and subsequently adopted by the United States Navy as the U.S. Navy utility knife, Mark 2. Additionally, Ka-Bar is the name of a related knife manufacturing company, Ka-Bar Knives., Inc. (formerly Union Cutlery Co.) of Olean, New York, a subsidiary of the Cutco Corporation.

Although Ka-Bar Knives, Inc. currently makes a wide variety of knives and cutlery, it is best known for the Ka-Bar Fighting/Utility knife, which has traditionally used a 7 in. (178 mm) 1095 carbon steel clip point blade and leather-washer handle.

The owner of the KA-BAR trademark, the Union Cutlery Co. of Olean, New York, began using the name on its knives and in its advertising in 1923 after receiving a testimonial letter from a fur trapper, who used the knife to kill a wounded bear that attacked him after his rifle jammed. According to company records, the letter was only partially legible; "ka bar" could be read, as fragments of the phrase "kill a bear". In 1923, the company adopted the name Ka-Bar from the "bear story" as their trademark. Beginning in 1923, the KA-BAR trademark was used as a ricasso stamp by Union Cutlery Co. on its line of automatic switchblade pocket knives, including the KA-BAR Grizzly, KA-BAR Baby Grizzly, and KA-BAR Model 6110 Lever Release knives.