Yolanda Hadid removed the last vestige of her marriage to David Foster with a legal name change ... TMZ has learned.

The former 'RHBH' star filed late last month to drop 'Foster' from her name, and she got a pretty quick answer. The judge signed off on her request on April 5 ... according to docs obtained by TMZ.

Yolanda and David's divorce was finalized in October of last year.

Interestingly, she's now officially back to using just her FIRST married name -- from Mohamed Hadid. Yolanda's maiden name is van den Herik but, let's be honest ... thanks to her daughters, Bella and Gigi, Hadid's the name to go with these days.