#1Lib1Ref (known in some Romance languages as #1Bib1Ref) is a Wikipedia campaign inviting librarians to participate in the online encyclopedia project, specifically improving articles by adding citations.

[1][2][3] Based on the premise of One Librarian, One Reference, organizers estimated that if each librarian on the planet spent 15 minutes adding a citation, the combined effort would eliminate English Wikipedia's backlog of 350,000 "citation needed" notices.

[4] The inaugural, weeklong event ran from 15–23 January 2016, and employed the hashtag #1lib1ref on various social media platforms.

[5] The inaugural campaign ended with 1,232 revisions on 879 pages, by 327 users in 9 languages, using the hashtag #1lib1ref in the edit summary; these numbers likely underestimate the overall impact, since many participants were observed omitting the hashtag from edit summaries.

[6] The campaign has been revived as an annual celebration of Wikipedia's birthday,[7] expanding into a three-week event in subsequent years.