Tony Romo's Building Insanely Expensive Mansion in Dallas

Tony Romo's upgrading in Dallas in a BIG way ... he's building a massive new home in a prestigious gated community ... and TMZ Sports has pics of the pad.

The Dallas Cowboys QB's new home is under construction on a 3 ACRE plot of land he purchased a few years back.

According to tax records, the land alone was valued at more than $4 MILLION when it was assessed in 2014.

As for the home itself, it looks huge ... public documents show it will boast 7 bedrooms, 7 bathrooms, 2 wet bars, 2 fireplaces, a pool with a cabana and much, much more!

Our sources say construction is about 3/4 of the way done.

Romo has listed his other Texas home -- a 5,551 square foot mansion for $1.05 million ... so we're guessing he plans to move in pretty soon.