ALN, AlN or Aln may refer to:
Alnus glutinosa, the common alder, black alder, European alder or just alder, is a species of tree in the family Betulaceae, native to most of Europe, southwest Asia and northern Africa.
Alnus rubra, the red alder, is a deciduous broadleaf tree native to western North America (Alaska, Yukon, British Columbia, Washington, Oregon, California, Idaho and Montana).
Alnashsky District (Russian: Ална́шский райо́н; Udmurt: Алнаш ёрос) is an administrative and municipal district (raion), one of the twenty-five in the Udmurt Republic, Russia.
Alnico is an acronym referring to a family of iron alloys which in addition to iron are composed primarily of aluminium (Al), nickel (Ni) and cobalt (Co), hence al-ni-co.
Alnitak, designated Zeta Orionis (ζ Orionis, abbreviated Zeta Ori, ζ Ori) and 50 Orionis (50 Ori), is a multiple star several hundred parsecs from the Sun in the constellation of Orion.