The Ikale Tahi's deserved win in their final Pool A match has lifted them four places to ninth, equalling the highest position occupied by their Pacific Island rivals Fiji and Samoa since the rankings were introduced in October 2003.
Tonga now sit one below France, who have dropped beneath Ireland, Wales and Argentina to eighth. This is the lowest position France have ever occupied, the last time being before they beat New Zealand 27-22 in Dunedin in June 2009.
Despite the fall by les Bleus, the quarter-finalists of the 2011 Rugby World Cup are also the top eight nations in the latest rankings in the order of New Zealand, South Africa, Australia, England, Ireland, Wales, Argentina and France.
Wales, whom Ireland meet in Wellington next Saturday, scored nine tries to overwhelm Fiji 66-0 in Hamilton and confirm their quarter-final berth as Pool D runners-up. The win over the 16th-ranked Fijians did not affect either side's rating.
Ireland beat Italy 36-6 at Otago Stadium on Sunday to create a piece of history, having never before finished top of their pool in a World Cup.
Ireland's fourth successive victory has pushed their advantage over Wales through the two-point barrier and with France's fall they are now the second highest northern Hemisphere nation, just behind fourth-ranked England.
IRB WORLD RANKINGS (as of Monday, October 3):
Last week's positions in brackets -
1(1) NEW ZEALAND 90.62 rating points
2(2) SOUTH AFRICA 86.71
3(3) AUSTRALIA 84.84
4(4) ENGLAND 84.54
5(6) IRELAND 83.14
6(7) WALES 80.73
7(8) ARGENTINA 80.28
8(5) FRANCE 79.72
9(13) TONGA 76.63
10(9) SCOTLAND 76.20
Follow the Ireland team in New Zealand on www.twitter.com/irfurugby.