Dimer may refer to:

• Dimer (chemistry), a chemical structure formed from two similar sub-units
  • Protein dimer, a protein quaternary structure
  • d-dimer
  • TH-dimer
• Dimer model, an item in statistical mechanics, based on domino tiling
• Julius Dimer (1871–1945), German chess master

• Dimery (botany), having two parts in a distinct whorl of a plant structure
• Di (disambiguation), a prefix
• Dymer (disambiguation)
• -mer, a suffix
• Oligomer
• Peierls transition, sometimes called dimerization