- D1 stands for Dimension One Spas
- D1 stands for First Diagonal (heart)
- D-1 stands for Dopamine Type 1 (neurotransmitter; also seen as D1)
- D1 stands for Dopamine Type 1 (neurotransmitter; also seen as D-1)
- D1 stands for Device State 1 (partial-sleep power-down mode, computing)
- D-1 stands for Day 1 Posthatch (laboratory chickens)
D-1