Thomas Ravenscroft (c. 1582 or 1592 until 1635) was an English composer, theorist and editor, notable as a composer of rounds and catches, and especially for compiling collections of British folk music.

He probably sang in the choir of St. Paul's Cathedral from 1594, when a "Thomas Raniscroft" was listed on the choir rolls; likely he remained there until around 1600, under the directorship of Thomas Giles. He probably received his bachelor's degree in 1605 from Cambridge.

Ravenscroft's principal contributions are his collections of folk music, including catches, rounds, street cries, vendor songs, "freeman's songs" and other anonymous music, in three collections: Pammelia (1609), Deuteromelia or The Seconde part of Musicks melodie (1609) and Melismata (1611). Some of the music he compiled has acquired quite extraordinary fame, though his name is rarely associated with the music: for example "Three Blind Mice" first appears in Deuteromelia. He also published a metrical psalter (The Whole Booke of Psalmes) in 1621. As a composer his works are mostly forgotten, but they include 11 anthems, 3 motets for five voices and four fantasias for viols.

In addition to his activities as a composer and editor, he wrote two treatises on music theory: A Briefe Discourse of the True (but Neglected) Use of Charact'ring the Degrees ... (London, 1614), and A Treatise of Musick, which remains in manuscript (unpublished).