| Brewery | Location |
|---|---|
| ONCO Fermentations | Tully, New York |
| Oncore Brewery | Swanton |
| One Barrel Brewing | Madison |
| One Mile End | London |
| One Trick Pony | Lansing |
| One Well Brewery | Kalamazoo, MI |
| One World Brewing | Asheville, North Carolina |
| Onion Pub & Brewery | Lake Barrington, Illinois |
| Only Child | Northbrook, IL |
| Onopa Brewing | Milwaukee, Wisconsin |
| Onsala Hantverks Bryggeri | Onsala, Sweden |
| Oosteke Brouwers | Gavere |
| Oozlefinch Beers & Blending | Fort Monroe, Virginia |
| Ope! Brewing Co. | West Allis, Wisconsin |
| Open Water Brewery | Knutsboda, Finland |