Signe Ida Katarina Hornborg (8 November 1862, Turku – 6 December 1916, Helsinki) was a Finnish architect.

Hornborg graduated as an architect in 1890 by special permission, as female students were not admitted to the school.

[2] After first embarking on active collaboration with Elia Heikel, she joined the agency of Lars Sonck.

[3] One of her most notable works is the Signelinna (also known as Nerwanderin talo or Nerwander House) in Pori (1892).

[4] Working in the national romanticism style, Hornborg also contributed to the design for the fire department building in Hamina, requiring no fee.