E621 may refer to:
Rail locomotives edit
- FS Class E.621, a 1947 Italian model
- E621, a 2013 Japanese E6 Series Shinkansen railcar
Other uses edit
- Monosodium glutamate, a food flavour enhancer (labelled E621 in the EU)
- e621.net, a booru-style furry fandom imageboard owned by the CEO of Bad Dragon