Smush Parker -- I Didn't Diss Kobe On Twitter ... THAT ACCOUNT IS FAKE!!!

Kobe Bryant IS NOT under attack from Smush Parker ... it's an IMPOSTOR posing as the former Laker who's VERBALLY DESTROYING Mamba on Twitter ... Smush tells TMZ Sports.

Social media went crazy after @SmushParker -- an account thought to be SP's -- attacked KB hours before his final game ... saying, among other things, "F*** OUTTA HERE KOBE"

FYI -- Bryant and Parker have beefed for years ... with Kobe famously saying, "Smush Parker was the worst. He shouldn't have been in the NBA."

In other words, people weren't shocked -- just really entertained -- when Parker dissed Kobe.

Here's the twist ... we reached out to Smush, and he's adamant the account is NOT his ... telling us, "Its definitely not mines. I would love to have that account deactivated.”

So, all's peachy with Kobe? Eh, maybe not ... we asked Smush to reflect on the Mamba's career.