6:02 PM PT -- Steph's video endorsement just played at the DNC ... and he says Harris is right for the Oval Office because she will unite America and move the country forward.

Wearing his gold medal from Paris, Steph explained why he believes Harris is the right choice for president in 2024 ... calling on folks to hit the polls in November like never before.

Kamala Harris is about to pick up an endorsement from an American hero ... Steph Curry!!!

The NBA star, who just led Team USA to a gold medal in basketball at the Paris Olympics, is going to endorse Harris for president with a surprise video message that will air Thursday during the Democratic National Convention ... DNC officials tell TMZ.

Curry's got a few connections to Harris ... they hung out this summer when Team USA was in Las Vegas preparing for the Olympics ... and Steph's played his entire NBA career for the Golden State Warriors, the home team for the San Francisco Bay Area and Oakland ... where Kamala was born and where she served as District Attorney.

Steph's NBA coach, Steve Kerr, previously gave a speech at this week's DNC in Chicago ... when he referenced his star player's signature celebration as a way to troll Donald Trump.

Kerr, who coached Curry to four NBA championships with Warriors and was the head coach of this year's Olympic team, raved about Kamala and her running mate, Tim Walz, for most of his nearly 10-minute speech and then ended with a shot at Trump.

"In the words of the great Steph Curry," Kerr said just before he put his hands in the shape of a pillow, "we can tell Donald Trump, 'Night, night!'"

It will be interesting to see what Steph has to say about the Harris-Walz ticket.

Stay tuned ...