'Spy Kids' Star Alexa Vega -- I'm a 23-year-old Divorcee Now!

After less than 650 days of marriage -- "Spy Kids" star Alexa Vega took a cue from Katie Holmes' playbook and officially pulled the plug on her marriage to a much older man, TMZ has learned.

The 23-year-old actress -- who played Carmen Cortez in the "SK" franchise -- filed docs in L.A. Superior Court recently ... citing irreconcilable differences with her 36-year-old husband Sean Covel.

In the docs, Vega lists the date of separation as March 5th, 2012 ... meaning the couple was separated for several months before the actress decided to legally axe the union.

Vega and Covel were married October 10, 2010 in South Dakota ... the actress was just 21 at the time -- but you can check her out (below) at age 6, starring opposite Rick Moranis in "Little Giants."

They grow up so fast.