Can I use my own ground coffee in a Keurig?

Yes, with a reusable K-Cup filter (sometimes called a My K-Cup) sold separately for most Keurig models including the K-Classic, K-Express, and K-Elite. Owners on r/keurig note that grind size matters: too fine clogs the needle, too coarse weakens extraction. Hybrid machines like the Ninja Pods & Grounds and Chefman Caffeinator have a dedicated grounds basket built in.