Cannabis in Oregon is legal for both medical and recreational use. In recent decades, the U.S. state of Oregon has had a number of legislative, legal, and cultural events surrounding use of cannabis. Oregon was the first state to decriminalize the possession of small amounts of cannabis, and among the first to authorize its use for medical purposes. An attempt to recriminalize possession of small amounts of cannabis was turned down by Oregon voters in 1997.

The use, sale, and possession of cannabis containing over 0.3% THC by dry weight in the United States, despite laws in many states permitting it under various circumstances, is illegal under federal law. As a Schedule I drug under the federal Controlled Substances Act (CSA) of 1970, cannabis containing over 0.3% THC by dry weight is considered to have "no accepted medical use" and a high potential for abuse and physical or psychological dependence. Cannabis use is illegal for any reason, with the exception of FDA-approved research programs. However, individual states have enacted legislation permitting exemptions for various uses, including medical, industrial, and recreational use.