Lūcijs (Lucius) Endzelīns (21 May 1909, Dorpat (Tartu), Estonia - 27 October 1981, Adelaide, Australia) was a Latvian-Australian chess master. Son of the Latvian linguist Jānis Endzelīns.
In 1932, Endzelins tied for 3rd-5th with Fricis Apšenieks and Movsas Feigins, behind Vladimirs Petrovs, and Teodors Bergs, at the Riga championship. He played for Latvia in three Chess Olympiads; on seventh board (+10 -6 =2) in the unofficial Olympiad at Munich 1936, as first reserve (+6 -2 =4) at Stockholm 1937, and on fourth board (+7 -5 =3) at Buenos Aires 1939. Married to the Latvian chess master Milda Lauberte (1918-2009).
At the end of World War II, Endzelins, along with many other Baltic players (Arlauskas, Dreibergs, Jursevskis, Mednis, Ozols, Sarapu, Tautvaišas, Vaitonis, Zemgalis, et al.), escaped to the west just before the advancing Soviet forces arrived. In 1946, he played in Augsburg. The event was won by Wolfgang Unzicker. In 1947, he won, ahead of Elmārs Zemgalis and Efim Bogoljubow, at the Mattison Memorial Tourney in Hanau, Germany. Lucius Endzelins migrated from Germany to Australia. He won the South Australian Championship eight times. He won the Australian championship in 1961.
Endzelins was awarded the Correspondence Grandmaster title in 1959. He tied for 2nd place, with Lothar Schmid, behind Viacheslav Ragozin, in the 2nd World Correspondence Championship, held from 1956 to 1959. He took 7th in the 3rd WCCh, held in 1959-1962, and tied for 7-8th in the 5th WCCh, held in 1965-1968.