It means the man who scored 1049 points for Wales, and a world record 1090 Test points overall, will face the player who has made 114 appearances for England, and a world record 118 Test appearances overall.
"It promises to be a pretty emotional ending to my career," said Jenkins, who last appeared at the Millennium Stadium when he made his 100th appearance in a Welsh jersey against the Barbarians last season. "It is a great honour to be given the chance to play a Testimonial match at the Millennium Stadium and I can think of no better opponent to have than English greatest forward, Jason Leonard.
"I've already dished out a few beatings to Jason down the years - well, just the two in 1993 and 1999 - and I'll be looking for the hat-trick to thrill what we both hope will be a big, family orientated crowd.
"The players we have invited to join us for this special celebration have all taken up the challenge enthusiastically and there should be plenty of entertainment for the crowd.
"It is not going to be a run around for the old boys - it is going to be a serious match. How could you ask Scott Gibbs and Scott Quinnell to play against Jason Leonard and a team wearing white shirts not to take it seriously!"
Jenkins's side will wear red shirts and Leonard's team will wear white. There will be some cameo appearances from some of Jenkins's team mates from the 1994 Five Nations Championship winning side and the 1999 team that won 10 games in a row. But perhaps the biggest thrill for Jenkins, and the fans, will be the chance to play one final match with his long standing half-back partner, Rob Howley.
"I played 34 times for Wales with Rob, and a lot more with Cardiff, and I was delighted when he agreed to have one last outing," said Jenkins. "He is still in world class form and has helped London Wasps reach the semi-finals of the Heineken Cup this season and become the dominant force in English rugby."
Scott Gibbs is also set to come out of retirement to join forces with the player with whom he came through the ranks of Welsh rugby. Having played together for Wales Youth in 1990, the two teenagers made their senior Welsh debuts against England at Cardiff Arms Park on 19 January, 1991. A certain Jason Leonard was in the front row for England that day as they ended a 28 year wait for a victory in Cardiff. That was Leonard's fourth cap, but his debut in the Five Nations championship.
"I can remember that game in Cardiff very well. It was a special day for me, too, because it was my first game for England in the northern hemisphere," said Leonard. "Although we've been big rivals down the years, I've got to know Neil very well on two Lions tours and we are also good friends. He's a legend in Wales, but also way beyond that.
"If you wanted someone in your side to kick the winning goal then you would look no further than the Ginger Monster. The only problem for me on 6 June is that he is going to be on the wrong side!
"It is a huge honour for me to be able to raise a side to bring to Cardiff, one of the rugby capitals of the world, to play against a Neil Jenkins XV. I'm sure we're all going to have a fun weekend, but this won't be a match either of us will want to lose."
The game will be played on the 60th anniversary of the D-Day Landings and as a mark of respect there will be a special dedication before the game to the 13 Welsh rugby internationals who were killed during the two Great Wars.
A Welsh slate plaque commemorating the fallen soldiers will be installed at the Millennium Stadium and a collection on the day will be made for the Royal Regiment of Wales.
"This is the first of what we hope will become an annual event at the Millennium Stadium," said Millennium Stadium general manager Paul Sergeant. "We are aiming at the family market for what will be a superb day out. There will be a special post-match party and plenty of value for money entertainment."
Among the stars on parade on 6th June 2004 will be:
Neil Jenkins XV
Jason Leonard XV
International stars Andre Vos, John Leslie, Thomas Castaignede, Kenny Logan, Craig Dowd and Paul Burke are also in line to make guest appearances.