Adelphia (from the root ἀδελφ- in Greek, forming ἀδελφός, adelphós, « brother » and ἀδελφή, adelphḗ, « sister »). designates the kinship between individuals born of the same parents. It does not bear any gender distinction, unlike fraternity, brotherhood, and sorority

The term comes from French feminism and emerged in the 2000s, in French adelphité. It aims at the inclusion of all genders in the concept of kinship solidarity. Feminist and queer campaigns in France fight for the modification of the national motto from Liberté, égalité, fraternité (“Liberty, egality, fraternity”) to Liberté, égalité, adelphité (“Liberty, egality, adelphia”). Fraternité, meaning brotherhood in English, is judged too sexist and exclusive of other genders, and as a national motto, it invisibilizes the presence and contribution of women (as well as non-binary and trans people) in French history and their participation in democracy.

In 2018, the Haut conseil à l’égalité entre les femmes et les hommes – a french independent consulative institution – suggested the replacement of “fraternity” in the national motto by “adelphity” or “solidarity” in its 4th recommandation.