Lilli Gjerløw (19 June 1910 – 4 December 1998) was a Norwegian archivist.
She was born in Nord-Audnedal as a daughter of vicar John Jenssøn Gjerløw (1856–1915) and Agnes Christine Boye. The family (after the father's death) moved to Arendal when she was young. She was a niece of Mons Klingenberg Gjerløw and Ragnvald Gjerløw and a first cousin of Olaf Gjerløw. From 1946 to 1949 she was married to Albert Lange Fliflet (1908–2001).
She finished her secondary education in 1929 in Arendal, and took an education in palaeography at the École Nationale des Chartes from 1932 to 1935. She then worked at the Norsk Historisk Kjeldeskriftinstitutt from 1935 to 1980. She took the dr.philos. degree in 1962 on the thesis Adoratio Crucis. The Regularis Concordia and the Decreta Lanfranci about the Regularis Concordia. Her specialty was the unveiling of medieval lithurgical texts from the countries around the North Sea. In the series Libri liturgici provinciae Nidrosiensis medii aevi she published volume two, Ordo Nidrosiensis Ecclesiae (Orðubók) in 1968, and volume three, Antiphonarium Nidrosiensis Ecclesiae in 1979. Her two-volume Liturgica Islandica from 1980 constitutes the volumes 35 and 36 of Bibliotheca Arnamagnaeana. She also studied the history of the Hebrides from 1952 to 1953 with a NAVF scholarship, and contributed to the encyclopedia Kulturhistorisk leksikon for nordisk middelalder. She was a member of the Norwegian Academy of Science and Letters from 1984.
She died in December 1998 in Oslo.