Dier or DIER may refer to:
- People
- Brett Dier (born 1990), Canadian actor
- Dirk Dier (born 1972), German tennis player
- Eric Dier (born 1994), English footballer
- Richard A. Dier (1914–1972), American judge
- Tobias Dier (born 1976), German golfer
- Other
- Department of Infrastructure, Energy and Resources, a former department of the Tasmanian government
- Wakker Dier, Dutch animal welfare organisation
- Department for Industrial & Employment Relations of Malta