NBA Star Rookie Ja Morant Surprises Dad With New Car, 'For You OG'

NBA Rookie of the Year? Nah, Ja Morant is flat-out SON of the Year ... 'cause the Memphis Grizzlies superstar just surprised his dad with a brand new car -- and it's awesome!!

The 20-year-old posted a vid of his new present for Pops on Wednesday ... and check out Dad's reaction -- dude couldn't even stand up straight he was so blown away!!

As for why ... the ride is pretty amazing -- it appears to be a new Dodge Charger SRT Hellcat, which goes 0 to 60 in about 3.6 seconds!!!

The ride -- which can come with up to 700 horsepower in the engine bay -- costs anywhere from $30,000 to $70,000 with all the bells and whistles ... so it's definitely a dope gift from Ja.

Of course, Morant owes a lot of his basketball success to his father ... Tee Morant -- who famously played high school ball with NBA legend Ray Allen -- was his main coach growing up.

In fact, Ja once said of his dad's basketball prowess, "He just knows what it takes ... Everything is really just a credit to him."