Ada Choi Siu-fan (Chinese: 蔡少芬; born 17 September 1973) is a Hong Kong actress best known for her work for TVB television, as an evil empress in the Chinese television series Empresses in the Palace (甄嬛傳), and to a lesser extent, for her film work.

Choi was born in 1973 in Hong Kong to a Chaozhou family. Her parents divorced when she was five years old. She speaks Cantonese, Mandarin, Teochow and English. In 1989, at the persuasion of her family, Choi participated in a modeling contest held by TVB at age 15.^[2] Two years later, she was a contestant in the 1991 Miss Hong Kong beauty pageant.^[3] During the semi-finals she placed first with an overall score of 483. She eventually finished as the second runner-up during the finals.^[4] As a result, she signed a contract with TVB and starting taking on acting jobs.^[5] She won the TVB Anniversary Award for Best Actress for her performance in Secret of the Heart (1998). Along with Maggie Cheung Ho-yee, Kenix Kwok, Flora Chan and Jessica Hsuan, Choi is known as one of the Top 5 "Fa Dans" (term used for actresses with high popularity) of TVB from the mid-1990s to mid-2000s. In 2009, she starred in Rebellion as a triad gang leader who chain-smokes and curses, a different type of role for Ada. In recent years, she has participated in numerous variety and reality shows as a regular cast member including Up Idol (2015), Run for Time (2015), My Dearest Ladies (2019) and Viva La Romance (2020).

On 12 January 2008, Choi married Chinese actor Max Zhang^[6][7] whom she had dated for more than four years. He was her co-star in a number of Zhouyi Media television productions including The Legend of Magic Mirror (2003) and Eight Charts (2005). They have two daughters, Zoe and Chloe, born in 2011 and 2013 respectively.^[8][9] In 2019, they announced on social media that they were expecting their third child. ^[10] They welcomed their son, Joey Zhang Le'er aka Yudan in November 2019.