The 29-year-old Reds winger, who won 100 caps and played in three World Cups during an 11-year international career, confirmed the widely-expected news at a packed press conference in Seoul on Monday.
Park had captained his country to third place in the Asian Cup, which came to a conclusion at the weekend with Japan beating Australia 1-0 after extra time in Qatar.
"I am announcing my retirement to open more doors for younger, junior players who have to grow to replace me eventually," he said.
"Like we have seen during the Asian Cup games, there are many young Korean players who have enormous potential, passion and talent.
"Just like I was given an opportunity for enormous growth during the 2002 World Cup, I think it is necessary to give good opportunities to junior players.
"My departure will help more young players who have demonstrated their talent and ability during the Asian Cup to prepare for the next World Cup."
Park’s decision is good news for United fans. Since missing nine months of action in 2007 he has suffered sporadic knee problems, and attributed these partly to long-haul flights from Manchester around the world.
Ji sat out Korea's third-place play-off win over Uzbekistan on Friday, though medical staff insisted this was precautionary.