Coalescence may refer to:
- Coalescence (genetics), the merging of genetic lineages backwards to a most recent common ancestor
- Coalescence (linguistics), the merging of two or more phonological segments into one
- Coalescence (physics), the merging of two or more droplets, bubbles or particles into one
- Coalescence (computer science), the merging of adjacent blocks of memory to fill gaps caused by deallocated memory
- COALESCE, a SQL command that selects the first non-null from a range of values
- Coalescence (chemistry), the process by which three separate masses of miscible substances seem to "pull" each other together should they make the slightest contact.