Who is the first cricketer to score a double century in an innings in one day cricket?

A double century (200 runs or more) in One Day Internationals (ODIs) has been scored on 6 occasions by 5 different batsmen from three of the ten Test-cricket playing nations. No player from Australia, Bangladesh, England, Pakistan, South Africa, Sri Lanka or Zimbabwe has scored 200.

The first ODI double century was achieved by Sachin Tendulkar for India against South Africa in 2010 during the second ODI of the bilateral series in Gwalior. The frequency of a batsman scoring an ODI double century is slightly less than that of a bowler taking a Test hat-trick (6 double centuries versus 39 hat-tricks as of August 2015).[2] The most double centuries by players from one country is four by India. Two double centuries have been scored in World Cup matches, both in the 2015 tournament.