Former Rams running back Isaiah Pead is learning to walk -- scratch that, he's already jogging -- in a brand new prosthetic leg ... with hopes of eventually achieving Paralympic gold.

Pead shared a vid of himself trying out his new running leg for the first time Friday, and while it looks like he's got some work to do to get the hang of it ... we know he's not gonna slow down 'til he does.

TMZ Sports spoke with Isaiah last month, and he told us he's on a quest to hit the track in the 2020, 2024 and 2028 Summer Paralympics ... and he'll be in it to win it.

He says his goal is to compete in the 400, an event he dominated as a high school sprinter.

As we reported ... Pead lost his left leg in a 2016 car crash, which ended his football career. But clearly his athletic career is far from over -- he's moving forward one step at a time.