On the eve of a major conference in Maputo that will bring together policymakers from across the region, Lagarde said it was time to kick start the "next phase of its economic development."
The sub-Saharan Africa region is expected to grow at more than five percent this year according to the IMF's latest projections, after similar growth last year.
But there was a note of caution amid the breakneck economic expansion.
"There is still a long way ahead to meet the aspirations of the continent: extreme poverty is still too prevalent and there are new challenges posed by the global economy," she said.
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The region could face lower demand for its exports should growth slow in increasingly important emerging markets like Brazil, India and, in particular, China.
Beijing is a top buyer of African resources from copper to oil and gas.
In rapidly growing cities like Maputo the Chinese presence is manifest, from a Chinese-built airport to the country's businessmen chattering on cell phones as they walk from meeting to meeting.