- MRI
- Mrozik Jennifer G
- Mrs Field's Cookies
- Mrs Field's Original Cookies
- Mrs Winner's Restaurants
- Mrs. Field's
- Mrs. Winners
- Msc Industrial Supply
- Msx International
- MTI
- MTS
- Muchas Gracias Mexican Food
- Mud Bay
- Mueller
- Muffler Brothers
- Muffler Center
- Muffler Doctor
- Muffler King
- Muffler Man
- Muffler Masters
- Muffler Shop
- Mufflers & More
- Mufflers 4 Less
- Mufflers for Less
- Mug Shots
- Muirlab-John Muir Medical Center
- Mulligan's
- Mulligan's Pub
- Multi Specialty Health Care
- Multicare Health Information and Provider Referral Line
- Multi-Financial Securities Corporation
- Multiple Listing Service
- Multiple Sclerosis Society
- Multi-Services
- Multistate Transmissions
- Multnomah Greyhound Park
- Munchies
- Mundelein Service Inc.
- Mundo Latino