1O
# 1O

1O or 1-O (the digit "1" and the letter "O") may refer to:

* 1o Sector, see Primary sector of the economy
* Glucogallin, or 1-O-galloyl-beta-D-glucose
* Isomalt, or 1-O-alpha-D-glucopyranosyl-D-mannitol
* Corilagin, or Beta-1-O-galloyl-3,6-(R)-hexahydroxydiphenoyl-d-glucose
* 2017 Catalan independence referendum, called for October 1, 2017, known as 1-O
