Chad Johnson Gifts Single Mom $1,000 Tip, 'Merry X-Mas!'

Chad Johnson did his best Santa Claus impression last weekend ... gifting a $1,000 tip to a single mother waitress -- and the gesture was awesome.

TMZ Sports has learned the ex-NFL star was dining at Bar Louie in Tampa, Fla. back on Nov. 26 -- and after piling up a $102 bill, he decided to get super generous.

The former Cincinnati Bengals wideout added a $1,000 tip to his total ... and when his waitress, Kayla Ashby, went back to him to make sure it wasn't a mistake, we're told he revealed to her it was no joke.

Ashby, we're told, thanked Chad ... and said afterward that she and her son, Zaith, are going to have a wonderful Christmas thanks in part to Johnson's generosity.

Of course, Chad's done this many times in the past ... the 43-year-old is known for leaving big tips every now and then.

As for the message he left to Ashby, Johnson wrote alongside the big tip, "Merry X-mas early. You can catch the Black Friday sales."

Johnson added, "'I love you.'"