琐罗亚斯德教（波斯文：زرتشتی‌گری‎），伊斯兰教诞生之前中东和西亚最具影响力的宗教，古代波斯帝国的国教。曾被伊斯兰教徒贬称为“拜火教”，在中国称为「祆教」或「白头教」。

琐罗亚斯德教的思想属西方理论定义下的二元论，有学者认为它对犹太教以及后来的基督教和伊斯兰教影响深远。琐罗亚斯德教的神“密特拉”也进入到罗马帝国以及印度的佛教的宗教之中。目前此教在伊朗偏僻山区和印度孟买一带的帕西人（又译作巴斯人）中仍有很大的影响力。

此教的创始人是琐罗亚斯德，出身于米底王国的一个贵族骑士家庭，20岁时弃家隐居，30岁时声称受到神的启示，破斥当时的多神教，宣说拜火教，但受到当时的多神教祭司的迫害。直到42岁时，阿契美尼德帝国的宰相娶他女儿为妻，将他引见国王，琐罗亚斯德教才在波斯迅速传播，77岁时他在一次战争中，在神庙中被杀身亡。另有说法琐罗亚斯德的生存年代要更早，琐罗亚斯德教也非他首创，有源自更远古的继承。

Zoroastrianism, or more natively Mazdayasna, is one of the world's oldest religions, "combining a cosmogonic dualism and eschatological monotheism in a manner unique... among the major religions of the world." Ascribed to the teachings of the Iranian Prophet Zoroaster (or Zarathustra), he exalted their deity of wisdom, Ahura Mazda, as its Supreme Being. Leading characteristics, such as messianism, heaven and hell, and free will influenced other religious systems, including Second Temple Judaism, Gnosticism, Christianity, and Islam. With possible roots dating back to the second millennium BCE, Zoroastrianism enters recorded history in the 5th-century BCE, and including a Mithraic Median prototype and Zurvanist Sassanid successor it served as the state religion of the pre-Islamic Iranian empires from around 600 BCE to 650 CE. Zoroastrianism was suppressed from the 7th century onwards following the Muslim conquest of Persia. Recent estimates place the current number of Zoroastrians at around 2.6 million, with most living in India and Iran. Besides the Zoroastrian diaspora, the older Mithraic faith Yazdânism is still practised amongst the Kurds.