Reese Witherspoon -- Good Bye 30's ... 40th Birthday Bash (VIDEO)

Reese Witherspoon will never have another birthday celebrating her 30's, but her big 4-0 was pretty epic.

Reese had #40 at Warwick in Hollywood Saturday night, and lots of celebs showed up, including Taylor Swift, Elizabeth Banks, Keith Urban, Nicole Kidman, Kate Hudson, Jason Bateman, Toby McGuire and Zoe Kravitz.

Reese turns 40 March 22nd.