The 40-year-old, who has enjoyed a glittering playing career at Old Trafford that has spanned three decades, is set to take charge of the team for the first time at the weekend following the sacking of David Moyes earlier this week.
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"I have got to say it is the proudest moment of my life," he said. "I have supported Manchester United all my life, I have been a part of the club since I was 13. I am proud, I am happy, a little nervous and, just like playing, can't wait for the game on Saturday.
"When Ed [Woodward] asked me to look after the team for the remaining four games, I had no hesitation in saying yes."
United sacked Moyes on Tuesday morning after a disappointing campaign that has seen the Premier League champion drop to seventh in the league table.
The Red Devils cannot qualify for next year's Champions League and will finish the year trophyless - with the exception of the Community Shield - but Giggs believes he can still rely on the players at his disposal.
"I've told the players 'I trust you and I know what you're capable of. Go out there and show it,'" he said, before confirming that he has a full-strength squad aside from Robin van Persie and Rafael to choose from.
"The players have looked great all week, they've looked sharp."