The new-look league will have 48 clubs in 12 groups of four, with the top two in each joining the eight third-placed clubs from the Champions League in a 32-club knock-out stage.
UEFA took the decision at their executive committee meeting in Bordeaux, and also ruled that beaten FA Cup finalists will no longer be eligible even if the cup winners have qualified for the Champions League - as has been the case with Millwall and West Ham in recent years.
A UEFA spokesman said: "The new format will result in many teams from all over Europe contesting the new UEFA Europa League, with teams from emerging countries or lesser known teams challenging the 'old' order of established European clubs.
"It is exactly this special character that the new identity will seek to capture."
The competition has TV rights sold centrally, in the same way as the Champions League, which should increase income to clubs.
UEFA president Michel Platini said: "I am convinced the new format will give the UEFA Europa League a successful new impetus."
UEFA are expected to formally confirm in December that Wembley will host the 2011 Champions League final.
The Government have confirmed an exemption to tax rules for players appearing in the final and the decision should be rubber-stamped by UEFA's next executive committee on December 16.
Dublin's Lansdowne Road is viewed as favourite to be named as venue for the 2011 Europa League final.
