Case of the Ex

"Case of the Ex" (sometimes subtitled "Whatcha Gonna Do") is a song by American singer Mýa. It was written and composed by Christopher "Tricky" Stewart and his songwriting partners Traci Hale and Thabiso "Tab" Nkhereanyne for Mýa's second studio album Fear of Flying (2000). The up-tempo pop and R&B track was inspired by a relationship Hale was going through at the time. It was released as the second single from the album, following "The Best of Me", on July 11, 2000.

The song received generally mixed reviews from contemporary music critics and was Mýa's breakthrough hit, both stateside and internationally. "Case of the Ex" became a top five hit on the US Billboard Hot 100 for the week of December 2, 2000, peaking and spending three consecutive weeks at number two. Internationally, the single topped the Australian ARIA Singles Chart for two consecutive weeks in March 2001 and peaked at number three in the United Kingdom.

The accompanying music video for the single was directed by Diane Martel. Mýa worked with choreographer Tina Landon, who later won an American Choreography Award for Best Hip Hop music video. The video drew comparisons to Janet Jackson's music video for "You Want This" (1994) and Mel Gibson's 1979 film Mad Max. In addition, the video was nominated for a Washington Area Music Award for Video of the Year, while the song itself won in the Urban Contemporary Recording category in 2001.