Frederick Clarke Withers (4 February 1828 – 7 January 1901) was an English architect in America, especially renowned for his Gothic Revival ecclesiastical designs.

Downing drowned a few months after Withers joined his office on July 28, 1852, attempting to save his mother-in-law in the explosion of the steamboat Henry Clay.

His library for the Frederick Deming House, "Morningside" (1859–60) was deemed architecturally significant by the Metropolitan Museum of Art in the late 1970s and removed for display.

One of Withers's most radical and linear villas of these years was "Tioronda" (1859–60), built for Joseph Howland and his wife Eliza Newton Woolsey in present-day Beacon, New York.

Set within a landscape by Henry Winthrop Sargent, Tioronda marked Withers's maturity as an architect and picturesque designer trained in Downing's vision.

His first commission in 1859 for a High Victorian Gothic building, the Reformed Church of Beacon (1860) was likely secured through the congregation's associations with John Peter DeWindt, his father-in-law.