The Office for the Coordination of Humanitarian Affairs (OCHA), an entity of the UN Secretariat, supports mobilization, coordination of humanitarian response to complex emergencies and natural disasters. OCHA is based in New York, Geneva and 30 regional and field offices.

OCHA operates a web site service, ReliefWeb, for the humanitarian community, to make relevant and reliable humanitarian information available through the internet. The site is managed and updated throughout a day, from New York, Geneva and Kobe, Japan.