Harriet (c. 1830 – June 23 2006) was a Galápagos tortoise (Geochelone elephantopus porteri) who had an estimated age of 175 years at the time of her death in Australia. Harriet is the second oldest tortoise ever authenticated, the oldest being Tu'i Malila, who died in 1965 at the age of 188.

Harriet is a female name. The name is an English version of the French Henriette, a female form of Henri. Compare with Harry that in a similar way is formed from Henry.