Roman Abramovich, whose British visa expired in April, has travelled to Tel Aviv where he is eligible for Israeli citizenship.
A spokesman for the 51-year-old would not confirm it has been granted, but Israel does offer citizenship to Jewish people wishing to move to the country.
Abramovich is a frequent visitor to Israel and owns property in Tel Aviv.
The Chelsea football club owner has been waiting several weeks for his UK investor visa to be renewed.
The delay comes amid strained diplomatic relations between London and Moscow.
Israeli passport holders can enter Britain without a visa for short stays.
The British and Israeli governments have declined to comment on the case.
Abramovich, whose net worth is said to be in excess of 12 billion Euros, bought the Chelsea football club in 2003 after making his fortune in oil.
If granted Israeli citizenship, he would be the richest person in the country.