In the latest ICC rankings released late Monday, Clarke leapfrogged Kumar Sangakkara of Sri Lanka and South Africa duo Hashim Amla and Jacques Kallis.
It is the third time Clarke has moved to the top of the table, having first achieved the ranking in August 2009 and then again surging to the summit in March-April 2012.
Both times his stay was brief, which could prove to be the case again.
He leads Sangakkara by a slender 10 rating points margin and if the Sri Lankan manages a strong performance in the second innings of the ongoing Test against New Zealand in Colombo, he could reclaim the coveted spot.
Clarke began the year in 20th position and has surged through the rankings by scoring 1,309 runs to date at an average of 119.
Despite struggling for top form in Australia so far, Proteas quick Dale Steyn held his No.1 Test bowling ranking ahead of Pakistan's Saeed Ajmal and South African Vernon Philander, who missed the Adelaide Test due to injury.
The drawn Test in Adelaide means Australia must win in the final Perth showdown starting on Friday to take the world number one ranking from South Africa.