Rosemary Theresa Theby (born Rose Masing,[1] April 8, 1892 – November 10, 1973) was an American film actress.

[4] A contemporary newspaper account described her as being of "medium-height, well proportioned, with regular features and dark hair".

[7] This was a femme fatale, or "vampire," role, which she began to play frequently after depicting characters in slapstick comedies.

[4] Theby played a Chinese "vamp" in Clung, a Fox Film production directed by Emmett J.

Theby enjoyed playing golf, wore her hair in a bob cut, and possessed a preoccupation with personal cleanliness.

[11] On screen she appeared tall and willowy, entering a scene, according to one review in the Los Angeles Times, with a "sensuous glide".