The 24 year old QB tells TMZ Sports he is officially engaged to GF Bre Tiesi ... the girl he's been dating since late 2016.

The two have been inseparable over the last few months -- and seemed to have really hit it off after a December trip to Miami.

Johnny tells us, "When you find a girl as amazing as I did that saved me from where I was in my life, you absolutely put a ring on it."

Manziel popped the question during a romantic trip to Paris -- with a MASSIVE diamond ring -- and a bouquet of roses.

Bre says, "I'm in shock. I couldn't imagine a day without [Johnny]. I'm so glad I never have to."

Tiesi is a model who also appeared as one of the hot chicks on the MTV show "Wild'n Out."

Congrats!