Paul Pierce says hes not done yet!!!!

NBA superstar Paul Pierce tells TMZ ... just because he left Boston doesn't mean his career's over -- he wants to play another TEN YEARS in the league!!

35-year-old Pierce was leaving a grocery store in L.A. with a bunch of water (it's important to hydrate) when we asked how he felt about being traded from the Celtics to the Brooklyn Nets this late in his prolific career.

Paul's reaction was CLASSIC -- "Who says it's the end of my career? I plan on playing ten more years dude."

We're not saying it's an impossible goal ... but it's gonna be pretty tough -- considering no one in the modern NBA era has played until the age of 45 (Dikembe Mutombo and Kareem Abdul-Jabbar played until they were 42 and Kevin Willis was 44).

Think he's got a chance?