Mainline Protestant

The mainline Protestants (sometimes also known as oldline Protestants) are a group of Protestant denominations in the United States and Canada largely of the theologically liberal or theologically progressive persuasion that contrast in history and practice with the largely theologically conservative evangelical, fundamentalist, charismatic, confessional, Confessing Movement, historically Black church, and Global South Protestant denominations and congregations. Some make a distinction between "mainline" and "oldline", with the former referring only to denominational ties and the latter referring to church lineage, prestige and influence. However, this distinction has largely been lost to history and the terms are now nearly synonymous.

Mainline Protestant churches have stressed social justice and personal salvation and, both politically and theologically, tend to be more liberal than non-mainline Protestant churches. Mainline Protestant churches share a common approach that often leads to collaboration in organizations such as the National Council of Churches, and because of their involvement with the ecumenical movement, they are sometimes given the alternative label of ecumenical Protestantism (especially outside the United States). While in 1970 the mainline Protestant churches claimed most Protestants and more than 30 percent of the American population as members, as of 2009^[update] they were a minority among American Protestants, claiming approximately 15 percent of American adults. In 2024, approximately 13.1% of Americans were white non-Hispanic mainline Protestants according to the Public Religion Research Institute's Census of American Religion.

The term mainline Protestant was coined during debates between modernists and fundamentalists in the 1920s. Several sources claim that the term is derived from the Philadelphia Main Line, a group of affluent suburbs of Philadelphia; most residents belonged to mainline denominations. Today, most mainline Protestants remain rooted in the Northeastern and Midwestern United States. C. Kirk Hadaway and Penny Long Marler define the term as follows: "the term 'mainline Protestant' is used along with 'mainstream Protestant' and 'oldline Protestant' to categorize denominations that are affiliated with the National Council of Churches and have deep historical roots in and long-standing influence on American society."

In the US, Protestantism is generally divided between mainline denominations and evangelical or theologically conservative denominations. The term is also occasionally used to refer to historic Protestant churches in Canada, Europe, Hong Kong, Latin America, and South Africa. The term has also been applied globally by researchers at Durham University. In some other parts of the world, the term mainline Protestant is not used. Instead, the term "ecumenical" is used to distinguish similar churches from evangelical denominations. Some have criticized the term mainline for its alleged White Anglo-Saxon Protestant ethnocentric and elitist assumptions, and its erroneous association with the term "mainstream" since it almost exclusively described White American, non-fundamentalist and non-evangelical Protestant Americans from its origin to the late twentieth century.

The term mainstream Christian in academic usage is not equivalent to mainline Protestant and is often used as an attempt to find impartial sociological vocabulary in distinguishing orthodoxy and heresy. Hence in Christological and doctrinal reference mainstream Christianity is often equivalent to Trinitarianism. Mainline Protestantism should not be confused with Nicene Christianity which is more widely accepted as having the "mainstream Christianity" designation that also includes Catholics, Eastern and Oriental Orthodox believers, and non-Mainline Protestants such as Evangelical, Fundamentalist, Charismatic, Confessional, Confessing Movement, the historically Black church, and Global South Protestants. In the United Kingdom and Australia, the term mainline Protestant is not always used, and mainstream does not mean progressive Protestant. Although some supporters and adherents do claim that Mainline Protestant is synonymous with Mainstream Protestant.

The largest mainline churches are sometimes referred to as the "Seven Sisters of American Protestantism," a term apparently coined by William Hutchison. The "Seven Sisters" are:

The term 'mainline' has also been applied to Canadian Protestant churches that share common origins with their US counterparts such as the:

The Association of Religion Data Archives, Pew Research, and other sources also consider these denominations, listed with adherents and members, to be mainline: