Mary Reid

• Mary Reid (activist), Irish activist, socialist and poet
• Mary Reid Macarthur, Scottish suffragist and trades unionist
• Mary Hiester Reid, American-born Canadian painter and teacher
• Mary Martha Reid, Florida's "most famous nurse and Confederate heroine"
• Mary Greyeyes-Reid, first woman of the First Nations to join the Canadian Women's Army Corps
• Mary E. Wrinch, British-Canadian artist

Fictional characters

• Mary Reid, in the UK TV soap opera Brookside, played by Carolyn Jordan