Alanna Ubach (born October 3, 1975 in Downey, California) is an American actress of Mexican and Puerto Rican descent.

Ubach began her career at the age of 4, playing alongside Henry Darrow in a small independent film, "Los Alvarez". At 17, she made a guest appearance on the television series The Torkelsons. She continued with television guest appearances and also appeared in the supporting cast of the film Sister Act 2: Back in the Habit. She then got her big break as co-star of the popular television program Beakman's World. She first found popularity with an adult audience as the lesbian Noreen in the film The Brady Bunch Movie.

A successful multi-episode 1996 guest spot on the show Party of Five and a critically praised performance in the independent film Clockwatchers which screened at Sundance and several art house theatres world wide. Ubach has guest starred in over 25 television shows while appearing in a number of independent pictures until her biggest mainstream success as Serena, best friend to Elle Woods in the film Legally Blonde. She also appeared in the film's 2003 sequel. By 2004 she appeared in over 46 films, including Meet the Fockers as Isabel.