Britt Reid -- Andy Reid's son and a former Kansas City Chiefs assistant coach -- has just been sentenced to three years in prison ... over his role in a 2021 car crash.

Britt learned his fate at a hearing inside of a Missouri courtroom on Tuesday afternoon ... a little over one month after he pleaded guilty to felony DWI in the case.

Britt showed up to the proceedings in a grey suit. He addressed the courtroom, according to The Kansas City Star, by apologizing and saying, "Every time I see my daughter, I think about Ariel and how my decision affected her so deeply and her family.”

The mother of Ariel Young, the 5-year-old who suffered serious injuries in the wreck, submitted a victim's impact statement ... which was read in court. It, in part, included the words, "There are 5 of us that Britt Reid's choice to drink and drive hurt."

Britt had been facing a maximum of seven years behind bars. He had petitioned the court in September for nothing more than probation.

As we reported, Britt was accused of drinking back on Feb. 4, 2021, getting behind the wheel of his pickup truck ... and then causing a serious car accident that left Young with life-changing brain injuries.

Authorities say Britt was going 83.9 MPH in a 65 MPH zone just before the wreck, and had a BAC of .113 two hours following the accident.

The 37-year-old was working for the Chiefs at the time, and was slated to coach during the Super Bowl against the Buccaneers just days later on Feb. 7.

But, he did not end up coaching in the contest, and departed from the org. a short time later. He has not been hired by an NFL team since.