Top Hollywood Agent -- Dumping Important Client ... His Wife!

It's an actor's nightmare ... being dumped by your agent.

Powerful Hollywood talent agent Sam Gores is in the process of splitting from his client -- and wife -- ex-soap actress Jensen Buchanan ... according to legal docs obtained by TMZ.

Gores -- who's chairman of the Paradigm Talent Agency -- filed for a legal separation from Buchanan ... they've been married since 2003.

Professionally, Buchanan is represented by Gores' agency, Paradigm ... although she's handled by another agent at the firm. No word on whether that professional relationship will change.

In his legal docs, Gores filed for separation based on irreconcilable differences ... and indicated he plans to pay spousal support. The docs also show the couple has a prenup.