Cymer or Cymmer may refer to:
- Cymer, Inc. a semiconductor company
- Cymer Abbey a Cistercian abbey in Wales
There are several places in Wales named Cymmer (standard Welsh: Cymer, meaning "confluence").
- Cymmer, Rhondda Cynon Taf, a village and community near Porth
- Cymmer, Neath Port Talbot, a village in the Afan Valley (also spelt Cymer)
- Cymer (Edeirnion) (sometimes spelt Cymmer), a place in Denbighshire