Mark Estes Jokingly Proposes Marriage to 'Love Island's Liv Walker, Video Shows

Mark Estes Offers Wedding Ring to Liv Walker ... After Hanging With Kristin Cavallari

Mark Estes was out and about in Tennessee on Sunday night ... yet he wasn't with his ex Kristin Cavallari, but rather another blonde bombshell, 'Love Island USA's Liv Walker.

The cohost of the "The Montana Boyz" podcast was chillin' with Liv and some friends in what appeared to be an outside seating area of a Nashville bar — and the two seemed really into each other.

In fact, as this TikTok video shows, Mark holds up a wedding ring and offers to marry Liv, who is offscreen shooting the footage with a camera.

Check it out ... After Mark's proposal, the camera swings to another woman, who screams "Yesssssss," as Liv says, "Look at my diamond baby."

Of course, this all appears to be a gag and done in good humor.

But, wait a minute -- our sources say Mark and Liv were also spotted together at Garth Brooks' Friends in Low Places & Honky Tonk Bar, also in Nashville.

We're told the two were sitting next to each other at a table with Mark's friends, aka The Montana Boyz, and some of Liv's buddies.

At one point, an employee walked out with a sign that read, "Liv's The New Montana Girl?"

Liv was at the bar with Mark when the sign arrived ... but her friends ran to get her and bring her back to the table.

All of this comes on the heels of Mark hanging out with his ex, Kristin, in Nashville last week ... TMZ obtained photos showing Mark and Kristin having a blast in a watering hole ... but our sources say they're just friends and not back together.