The Head Of The Charles Regatta, also known as HOCR or HOTC, is a rowing race held on the penultimate complete weekend of October (i.e., on the Saturday that falls between the 17th and the 23rd of the month, and on the Sunday right afterwards) each year on the Charles River, which separates Boston and Cambridge, Massachusetts. The race is named the "Head" of the Charles because it is a head race. It is the largest 2-day regatta in the world, with nearly 9,000 athletes rowing in over 1,900 boats in 61 events.