In cryptography, LOKI89 and LOKI91 are symmetric-key block ciphers designed as possible replacements for the Data Encryption Standard (DES). The ciphers were developed based on a body of work analysing DES, and are very similar to DES in structure. The LOKI algorithms were named for Loki, the god of mischief in Norse mythology.

In Norse mythology, Loki Anglicized , Loptr, or Hveðrungr is a god or jötunn (or both). Loki is the son of Fárbauti and Laufey, and the brother of Helblindi and Býleistr. By the jötunn Angrboða, Loki is the father of Hel, the wolf Fenrir, and the world serpent Jörmungandr. By his wife Sigyn, Loki is the father of Narfi and/or Nari. By the stallion Svaðilfari, Loki is the mother—giving birth in the form of a mare—to the eight-legged horse Sleipnir. In addition, Loki is referred to as the father of Váli in the Prose Edda.