The Millennium Stadium will host the 2006 Heineken Cup final on 20 May.
The Millennium Stadium last hosted the final in 2002
Cardiff has staged the showpiece club final on three previous occasions, twice at the old Arms Park and once at the Millennium Stadium.
The 2002 event holds the record for a Heineken Cup final attendance when 74,600 packed in to watch Leicester beat Munster by 15-9.
The news will be a boost for the stadium, with the FA Cup final expected to return to Wembley next year.
"The partnership approach adopted by Cardiff was exactly what we were looking for as we seek to continue the growth of our main event as one of Europe's top sporting occasions," said European Rugby Cup chief executive Derek McGrath.
"ERC worked closely with the city of Cardiff to broaden the appeal of the final when it was last at the Millennium Stadium in 2002 and we were rewarded with our biggest attendance.
"Our final this weekend in Edinburgh is set to generate £30m for the Scottish economy and we would expect to have as big an impact on the Welsh economy over the next year."
Building on the success of the giant screen used in the city centre for Wales' Grand Slam game with Ireland, Cardiff Council say they are planning a series of events to accompany the final.
Heineken Cup 2005/2006 fixture dates
Weekend 1: 21 / 22 / 23 October
Weekend 2: 28 / 29 / 30 October
Weekend 3:9 / 10 / 11 December
Weekend 4: 16 / 17 / 18 December
Weekend 5: 13 / 14 / 15 January
Weekend 6:20 / 21 / 22 January
1 / 2 April
22 / 23 April
20 / 21 May (Millennium Stadium, Cardiff)