Osman Hassan Ali Atto (Somali: Cismaan Xasan Cali Caato) (born 1940) is a Somali warlord, affiliated with the Somali National Alliance. He is a member of the Somali Hawiye clan, sub-clan Habar Gedir (sub-clan Sa'ad and the hiloowle and was born in 1945. Atto is his nickname meaning "skinny". Osman Ali Atto is a former main financier of the Aidid faction, a multi-millionaire businessman, alleged arms dealer and drug trafficker. Atto owns the biggest landed property in Somalia, including many of the buildings in Mogadishu which are rented to relief agencies and the media. Before the Civil War, Atto was a chauffeur to various representatives for the US oil company Conoco.