The Maryland Toleration Act, also known as the Act Concerning Religion, the first law in North America requiring religious tolerance for Christians. It was passed on April 21, 1649, by the assembly of the Maryland colony, in St. Mary's City in St. Mary's County, Maryland. It created one of the pioneer statutes passed by the legislative body of an organized colonial government to guarantee any degree of religious liberty. Specifically, the bill, now usually referred to as the Toleration Act, granted freedom of conscience to all Christians. Historians argue that it helped inspire later legal protections for freedom of religion in the United States. The Calvert family, who founded Maryland partly as a refuge for English Catholics, sought enactment of the law to protect Catholic settlers and those of other religions that did not conform to the dominant Anglicanism of Britain and her colonies.

Religious tolerance or religious toleration may signify "no more than forbearance and the permission given by the adherents of a dominant religion for other religions to exist, even though the latter are looked on with disapproval as inferior, mistaken, or harmful". Historically, most incidents and writings pertaining to toleration involve the status of minority and dissenting viewpoints in relation to a dominant state religion. However, religion is also sociological, and the practice of toleration has always had a political aspect as well.