The legalization of marijuana is the process of developing laws that allow for the use, possession, and/or distribution of marijuana based upon an established set of regulations. The legalization of medical marijuana allows the use of cannabis only by those with medical authorization. Adult use legalization, also known as recreational, allows the use of cannabis for people over a certain age, typically 21 in states where legal. Marijuana laws differ between states and countries.

Even though marijuana has been used for centuries, many countries started to criminalize its usage during the 19th century. The United States banned marijuana in 1937, and it is still considered illegal at the federal level. In 1996, California was the first state that legalized marijuana for medical use, and many states followed thereafter. Washington and Colorado both were the first states to legalize marijuana for adult, recreational use in 2012. Since then, as of March of 2023, 21 states have legalized cannabis for recreational use.

Uruguay was the first country to legalize adult-use cannabis in 2013, and Canada legalized adult-use cannabis in 2018. In some states that have not yet legalized recreational marijuana, they may have decriminalized it, which is different. Decriminalization means that a person would not be prosecuted or charged with a criminal violation for possession of under a certain amount. Legalization allows for the regulated cultivation and sale of marijuana, making it accessible to adults.