In human genetics, Haplogroup O3 (M122) is a Y-chromosome haplogroup.
This haplogroup appears in over 50% of all modern Chinese men, and is not found outside East Asia.
Haplogroup O3 is a descendant haplogroup of haplogroup O. It it believed to have first appeared in China approximately 10,000 years ago. Its spread is conjectured to be closely associated with the sudden agricultural boom associated with rice farming.