"反民族主义"（或称"反国族主义"或"反国家主义"）是指反对视自己民族最高尚的思想或认为自己民族特殊和优越于其他民族的狭隘民族身分认同思想。

反民族主义是一种反对对民族、种族、与国家等概念狭隘认同、极端捍卫的意识形态，该主义主张“人类都是一家人”的「基本思想」。通俗地说，反民族主义主张：人类都是同一物种，不应该刻意地以文化认同来作为国家存亡的基础，以及「各民族有平等行使义务之权」。类似的思想有世界政府和地球联邦之类的提议，以“人类共荣”而非“民族兴盛”作为基础的思想。

Anti-nationalism denotes the sentiments associated with an opposition to nationalism. Some anti-nationalists are humanitarians or humanists who pursue an idealist view of world community, and self-identify as world citizens. They reject chauvinism, jingoism and militarism, and want humans to live in peace rather than perpetual conflict. The imposition of nationalism as a belief or identity system, particularly when in conflict with more established and self-sustaining identity choices, often based on freely chosen religious or cultural beliefs and practices can be understood to undermine the legitimacy of territory-based nationalism. They sometimes do not necessarily oppose the concepts of countries, nation states, national boundaries, cultural preservation and identity politics.