Leave it to former Dallas Cowboys defensive end Greg Ellis ... who wrote and stars in a play about the holiday!

Ellis -- who spent 11 seasons with the Cowboys -- is now fully immersed in the theater world ... where he writes, produces and acts.

In fact, he created "Juneteenth The Stage Play" back in 2018 ... and has an upcoming performance this weekend.

44-year-old Ellis told CBS 11 in Dallas the focus on the play is to inform the audience about the history of Juneteenth in an entertaining way.

"A lot of people don't know the history," Ellis said ... "and so through our production, our challenge is to make sure it's accurate, make sure people can be entertained -- laughing, crying, happy, upset and all those emotions getting touched upon for one common good and that common good is that you're going to retain the information that's inside the play."

Now, Ellis says he's pushing to turn Juneteenth into a national holiday -- he even started a petition.

"Juneteenth celebrates the anniversary of June 19, 1865, which marks the end of African-American slavery in the United States. It is our belief that Juneteenth needs to be a national holiday and making it one right now would be a huge step in the right direction to start the healing process."