Elsevier B.V. (Dutch pronunciation: [ˈɛlzəvir]) is a publishing company which publishes medical and scientific literature. It is a part of the Reed Elsevier group. Based in Amsterdam, the company has operations in the United Kingdom, USA, and elsewhere.

Elsevier took its name from the Dutch publishing house Elzevir, which, however, had no connection with the present company. The Elzevir family operated as booksellers and publishers in the Netherlands. Its founder, Lodewijk Elzevir (1542–1617), lived in Leiden and established the business in 1580. The modern company was founded in 1880. Leading products include journals such as The Lancet and Cell, books such as Gray's Anatomy, the ScienceDirect collection of electronic journals, the Trends and Current Opinion series of journals, and the online citation database Scopus. Its free researcher collaboration tool, 2collab, launched in 2007, was discontinued in 2011.

Elsevier publishes 250,000 articles a year in 2,000 journals. Its archives contain seven million publications. Total yearly downloads amount to 240 million. The company is currently being boycotted by academics who object to its business model, which includes "paywalls" and (in their opinion) excessively high subscription charges.