Orthodox, Orthodoxy, or Orthodoxism may refer to:

• Orthodoxy, adherence to accepted norms, more specifically adherence to creeds, especially within Christianity and Judaism, but also less commonly in non-Abrahamic religions like Neo-paganism or Hinduism

• Eastern Orthodoxy, the world's second largest Christian denomination
• Oriental Orthodoxy, which does not accept the theological resolutions of the Council of Chalcedon

• Lutheran orthodoxy, an era in the history of Lutheranism which began in 1580 from the writing of the Book of Concord
• Neo-orthodoxy, a theological position also known as dialectical theology
• Orthodox Presbyterian Church, a confessional Presbyterian denomination located primarily in the northern United States
• Paleo-orthodoxy, (20th–21st century), a movement in the United States focusing on the consensus among the ecumenical councils and church fathers
• Reformed Orthodoxy (16th–18th century), a systematized, institutionalized and codified Reformed theology
• True Orthodox church, also called Old Calendarists, a movement that separated from the mainstream Eastern Orthodox Church in the 1920s over issues of ecumenism and calendar reform

• Proto-orthodox Christianity, a term coined by New Testament scholar Bart D. Ehrman to describe the Early Christian movement which was the precursor of Christian orthodoxy

• Orthodox Judaism, a branch of Judaism
  • Haredi Judaism, groups within Orthodox Judaism that reject modern secular culture
    • Hasidic Judaism, a sub-group within Haredi Judaism noted for its religious conservatism and, typically, social seclusion
  • Modern Orthodox Judaism, is a movement within Orthodox Judaism
• Kemetic Orthodoxy, an Egyptian neo-pagan religion that intends to reform and restore ancient Egyptian religion
• Orthodox Bahá'í Faith, a small Baha'i denomination
• Orthodox Hinduism, a term for Sanātanī
• Orthodox Islam, generally refers to Sunni Islam
• Slavic Native Faith or Orthodoxy, a term used by Neo-Slavic pagan religious organizations

• Left-arm orthodox spin, a bowling technique in cricket
• Orthodox (album), a 2013 album by American rock band Beware of Darkness
• Orthodox (band), an American metalcore band from Tennessee.
• Orthodox File Managers, a user interface to work with file systems
• Orthodox (Jordan), a Jordanian basketball club
• Orthodox Marxism, the dominant form of Marxist philosophy between the death of Karl Marx and the beginning of World War I
• Orthodox seed, a seed which may be preserved via drying or freezing
• Orthodox stance, a way of positioning the feet and hands in combat sports

• Anti-Orthodox (disambiguation)
• Heterodoxy
• Orthodox calendar (disambiguation)
• Orthodox Church (disambiguation)
• Orthodox Communion (disambiguation)
• Orthodoxy by country (disambiguation)
• Unorthodox (disambiguation)