Clementina "Kit" Caroline Anstruther-Thomson (15 December 1857 – 7 July 1921) was a Scottish author and art theorist.

[3] Anstruther-Thomson first met Vernon Lee in 1888, and for the next twelve years the two women openly lived together, as "lovers, friends, and co-authors".

[12] Many of the findings, however, were not taken seriously as both their professional and romantic relationship was "attacked"[13] by their contemporaries, receiving "severe criticisms" from friends.

[9] After the publication of "Beauty and Ugliness", Anstruther-Thomson gradually drifted away from Lee, and eventually broke off the relationship in 1898.,[10] remaining close friends.

[9] She was subsequently in a relationship with the Welsh author and Chief Commissioner for Girl Guides in Wales, Hon.

She was a paid-up member of the West London Ethical Society, a predecessor group of Humanists UK, which later recalled her contributions as one of its "heroines of freethought".