Alder is the common name of Alnus, a genus of shrubs and small trees.

Alder may also refer to:

• Alder (surname)

• Alder, Colorado
• Alder, Montana, United States
• Alder, Washington, United States
• Alders Brook, a small tributary of the River Roding
• Alder Creek (disambiguation)
• Alder River, Nova Scotia, Canada
• Des Aulnes River (Laflamme River) (English: Alders River), Quebec, Canada

• Alder (crater), lunar crater
• Alder (Pendragon series), a fictional character in The Pendragon Adventure
• Dwarf alder (disambiguation), common name of several plants
• Witch alder, plants of genus Fothergilla
• A shortened form of Aldernalisuvara, an alternative name of the Hindu deity Ardhanari particularly used by Japanese
• Alder (Pokémon), the champion of the Unova League in Pokémon Black and White
• Alders (surname)

• Alda (disambiguation)
• Elder (disambiguation)