Horgan made his debut for the Ireland senior side against Scotland in the 2000 Six Nations Championship, scoring a try in the process. In the following game against Italy he scored 2 tries and added another one against Wales during the tournament. He was selected for the 2005 British &amp; Irish Lions tour to New Zealand. He was used as a substitute during all three tests. After scoring the winning try against England at Twickenham in the 2006 Six Nations Championship to secure the Triple Crown for the second time in three years, he became a new national hero. Horgan added to his following in 2007 when he scored a try against England in Croke Park by executing a Gaelic football style catch from a Ronan O'Gara crossfield kick. Horgan is known by the Irish media and rugby fans as "Shaggy".