Tinsley Mortimer (née Tinsley Randolph Mercer in 1976) is a Manhattan socialite. She is married to Robert "Topper" Mortimer, a hedge fund manager. Described as "one of the most famous faces of the New York scene", the "much photographed" and "New York's pre-eminent young socialite"'s lifestyle and fashion are often commented and discussed in social pages of periodicals such as the New York Times, the New York Post, and New York Magazine. Mortimer has a popular line of handbags and clothing in Japan for Samantha Thavasa, for which she was featured in an extensive ad campaign. Recently, she has become involved in branding and design for condominium development.

Tinsley also recently had a cameo appearance on the season two premiere episode of Gossip Girl. , which aired September 1st, 2008 on The CW.

Mortimer graduated from Columbia University, where she was a member of St. Anthony Hall. She met her husband at the Lawrenceville School.