55-year-old Sharon Simmons of Carrollton, Texas is a single mother and a grandmother of two ... and on Saturday, she tried out to become a DALLAS COWBOYS cheerleader!

Now, she doesn't look like a stereotypical grandmother.  She's been entering fitness competitions since she turned 50 and has won nine of the 20 she's entered.

Anyway, Sharon tried out to become a Cowboys cheerleader along with hundreds of other women.  She says she actually forgot her routine but improvised okay.

Right now, the oldest cheerleader in the NFL is 43-year-old Laura Vikmanis, who's a cheerleader for the Cincinnati Bengals.

There's one last point that most of the media is dancing around, since this is a feel-good story ... but we're not afraid of the truth:  While it's impressive that Sharon tried out, she didn't get a callback, so she won't be a Cowboys cheerleader.