- Emil Abderhalden, (18771950), Swiss chemist
- Richard Abegg, (18691910), German chemist
- Arthur Aikin, (17731855), English chemist and mineralogist
- Johan August Arfwedson, (17921841), Swedish chemist
- Svante Arrhenius, (18591927), Swedish chemist and physicist
- Amedeo Avogadro, (17761856), Italian physicist

