Olympic champion Dibaba who is now unbeaten in her 11 outings over the distance won in 30:43.35.
Kenya's Gladys Cherono was second in 30:45.17 and fast-finishing Ethiopian Belaynesh Oljira pipped Emily Chebet for bronze in 30:46.98.
Arguably the greatest women's distance runner, Dibaba also won the 10,000 in 2007 and did the distance double at the 2005 worlds.
Long-time race leader Hitomi Niiya of Japan bravely pushed the pace as lightning flashed over the Luzhniki stadium and heavy rain began to fall.
Her Herculean efforts had whittled the leading group down to herself and the four Africans at the bell, but Niiya was no match for Dibaba in full flow and she was left trailing home in a distant fifth.
(Writing by Alison Wildey; Editing by Martyn Herman)
