Ireland is one of the world's top international rugby teams, so they have and have had many famous players. Players like the current captain, in March 2015, Paul O'Connell and the recently retired Brian O'Driscoll, and many, many others.
brian o'driscoll ronnon o'gara
The Lions are the touring rugby side which is made up of players from England, Scotland, Wales and Ireland
for rugby league it is 13 players and for rugby union it is 15 players
There are 122,598 registered rugby union players in japan.
None of the top players most play in Ireland with a few in England
13 ... there are 13 players in rugby league and 15 players on a rugby union team
The number of players in a Rugby League match is 15
Ireland has many rugby teams. However, what you are probably referring to is why there is not a Republic of Ireland and a Northern Ireland team. The reason is that, like many sports in Ireland, rugby is played on an all-Ireland basis and there one organisation that looks after it, the Irish Rugby Football Union, and so there is one international team.
The main league in Ireland is called the All Ireland League which was founded in 1990. In total there are 51 rugby clubs in Ireland.
Professionally there are about 100. Altogether there are 20,000 teenage and adult men who play. Tag rugby is hugely popular though, has about 4 times that number.