The Secrets of Sir Richard Kenworthy is a Regency romance written by Julia Quinn and published in 2015 by Avon Books.

[1][2] Her twenty-fourth novel,[3] The Secrets of Sir Richard Kenworthy, is the fourth and final book in Julia Quinn's Smythe-Smith Quartet.

After seeing Iris Smythe-Smith perform, Sir Richard Kenworthy finagles an introduction and begins a flirtation.

After the wedding, Sir Richard uses a series of excuses to postpone consummating the marriage, to Iris's dismay.

Writing for Kirkus, Bobbi Dumas noted that in the Smythe-Smith Quartet Quinn has maintained her "signature bright, buoyant voice" while still exploring darker themes.

[1] In Booklist, John Charles wrote that the novel showcases Quinn's "sparkling wit" and includes enough "seductive passion to create another swoon-worthy love story".