Cristiano Ronaldo's Girlfriend Georgina Flashes Massive Diamond Ring

Cristiano Ronaldo hasn't officially said he's engaged to baby mama Georgina Rodriguez ... but her diamond ring was doing A LOT of talking at the Portugal game Wednesday in Russia!

There's been a lot of talk CR7 proposed to her back in April -- just months after she gave birth to their daughter, Alana Martina, back in November.

Well, Wednesday at the World Cup ... Georgina flaunted the ring for everyone to see.

Wasn't hard to spot ... the diamond is the size of her knuckle.

Meanwhile, Ronaldo killed it on the pitch ... scoring the only goal to help Portugal defeat Morocco, 1-0.