"After eight years I will not stay any longer," Del Ponte was quoted by the Reuters news agency as saying on Tuesday.
"I think it is the right time to leave," a Swiss lawyer who turns 60 next month, told foreign journalists on Tuesday.
Del Ponte became the tribunal's third chief prosecutor in 1999, after South Africa's Richard Goldstone and Canada's Louise Arbour, but has served two terms and become synonymous with the court's attempt to arrest and try its highest-profile fugitives.