Mike Piazza is getting hitched.

The Mets catcher is walking down the aisle with his longtime girlfriend, "Baywatch" babe and former Playboy Playmate Alicia Rickter (search), in Miami during the last weekend in January, sources said yesterday.

"It is going to be a very small wedding, just family and close friends," said a pal.

The wedding will most likely take place on Sunday, Jan. 30, but Rickter and Piazza will have their bachelorette and bachelor parties a night or two before.

"Alicia and her friends are going to a club in South Beach, while Mike is going to a dinner with a bunch of close friends, where he will be roasted mercilessly," the couple's pal said.

The wedding will be "a very long weekend event that will be a lot of fun."

Piazza's representative refused to comment yesterday.

The duo met in October 2002, and Rickter, a former Playboy Playmate, quickly tamed the catcher's famous wandering eye.

The beautiful brunette was a Killian's beer spokesmodel at the time, while Piazza was often seen around town with beautiful women. He was known to have homered with a bevy of babes, including another veteran of Playboy's pages, Darlene Bernaola (search).

But he's been off the market since getting serious about Rickter — and his life.

"The first part of my life was totally focused on baseball, but I've grown up a little," Piazza told Playboy in 2003.

"Living through Sept. 11 in New York, that has to change you. I'm thinking the next chapter is settling down, starting a family," he said to the magazine.

Around the same time, Rickter told the Post: "I want a big family and I want work that won't make me travel so much. I am looking forward to a lot of kids — I am just a girl from Long Beach [California]."

The two are self-described homebodies — and metalheads, who love hard rock — although Piazza sometimes hits the clubs as hard as he hits baseballs.

He used to be a regular at Manhattan hotspot Lotus until Mets players started boycotting it after one of the team's second-stringers was refused entrance.

The night before Piazza broke the all-time home-run record for catchers last year, he was spotted partying at One in the Meatpacking District (search).

Piazza recently bought a $4 million condo in TriBeCa, but it's not known if the couple will shack up there after they've tied the knot.

The marriage should finally put an end to those unfounded rumors that Piazza is a switch-hitter. During the 2002 season, the perennial All-Star called an unprecedented news conference to explicitly state he was not gay.

"The truth is that I'm heterosexual and date women," he said.

Bernaola, the former Playmate of the Millennium, knew it all along.

"Our sex life was very, very healthy," she said at the time.

Beyond that, the couple also shared a cutesy pre-game ritual: Piazza would bite a Halls cough lozenge in half, and share it with Bernaola.