Deltic may refer to:
- Napier Deltic, a diesel engine
- British Rail DP1 ("Deltic") a prototype locomotive built by English Electric fitted with the Deltic Engine
- British Rail Class 55, production locomotives powered by Deltic engines
- British Rail Class 23, "Baby Deltic" production locomotives powered by Deltic engines
- Deltic acid, a chemical whose molecular backbone resembles the Greek letter delta (Δ)