Matthew Montgomery (born November 16, 1975), also known as Piggy D., is an American musician most famous as a guitarist in horror punk band Wednesday 13^[3] and bassist for Rob Zombie.

He first took over bass duties with Rob Zombie from current Ozzy Osbourne bassist Blasko, playing "American Witch" live on the Late Show with David Letterman right before picking up the second leg of the Educated Horses tour in mid 2006. To this day, he maintains a successful solo career while playing with Zombie.

Mr. Piggy co-directed a short 10-minute promo video entitled Along Came a Spider: the Movie for Alice Cooper's album which was released on the Cooper's official YouTube-page on October 2, 2008. The movie featured three songs from the album: "Vengeance is Mine," "(In Touch with Your) Feminine Side", and "Killed by Love." The video stars Alice Cooper, Slash, Roxxi Dott, Howie Pyro, and Dave Pino. Piggy D. also contributed all the graphic design for the album including the album cover and multiple teaser posters. Piggy D has also contributed album artwork for John 5's solo albums. His work features on Remixploitation (2009), Requiem (2008) and The Devil Knows My Name (2007). Piggy D also co-designed the art for the newest Lita Ford album Wicked Wonderland.

In 2009, Piggy co-wrote and produced the first ever Alice Cooper Halloween song, "Keepin' Halloween Alive." The single was released digitally on iTunes, and a limited edition CD. A glow in the dark 7" record has also been released.

February 2010 saw the release of the first studio album with Zombie that featured Piggy. The song "The Man Who Laughs" was co-written by Piggy.

In 2011, Piggy co-wrote with David Spreng, Bob Ezrin and Alice Cooper for the long waited sequel Welcome 2 My Nightmare. The track "Last Man On Earth" is featured on the album.

Piggy and vocalist Shannon Gallant began working together again after a 5-year hiatus, and began work a new recording project called The Haxans. The duo have released two singles "Cold Blood" and "Black Cat Bone."

In 2011, Piggy was invited to co-write and co-produce the debut album for The Doom Party. A release date has not been set.

In 2013, Piggy contributed to the song writing for the new Rob Zombie album Venomous Rat Regeneration Vendor with the song "Lucifer Rising". Piggy uses ESP basses.

In 2016, Piggy announced that he was collaborating with Ash Costello from New Years Day on a new project called The Haxans. The first single "Chains" was released on June 6, 2016.

In January 2024, Piggy D announced he was leaving Rob Zombie's band after 18 years.