The four-times world lightweight champion has played a major role in women's boxing, winning a place at the Olympics for the first time in London where she is Ireland's best hope of a gold medal.
One of the country's most popular athletes, the 26-year-old's appointment to the role was well-deserved, according to Irish Amateur Boxing Association chief Tommy Murphy.
"It's a great honour for Irish amateur boxing and we are absolutely delighted that Katie has been chosen to be the flag bearer for Ireland for the opening ceremony for the London Olympics," he said in a statement after the Olympic Council of Ireland confirmed the decision.
"She is the first female boxer to represent this country at the Olympic Games and it is a good choice. Katie is a fantastic ambassador for our sport and her record in international competition speaks for itself."