Barrie McKay was Forest's main threat throughout and marked his full debut with the winner
Barrie McKay's spectacular debut strike earned Nottingham Forest an opening-day win against a Millwall side who wasted numerous chances.
The Lions dominated, with Steve Morison crashing an effort against the bar and Aiden O'Brien and Lee Gregory missing glorious first-half opportunities.
But McKay's long-range shot put the Reds ahead at half-time.
And although Millwall's direct approach continued to pose problems, the Reds somehow held on for victory.
Forest's fifth first-day win in their past six seasons looked highly unlikely as last season's League One play-off winners created chance after chance before the break.
Morison should have scored with a close-range shot, O'Brien wasted three headed chances while Reds keeper Jordan Smith was in superb form, notably when he kept out Gregory's low shot.
After the equally outstanding McKay, one of three of six Forest summer signings to start, fired in the opener Forest continued to lead a charmed life.
Morison found the back of the net in the second period, but his strike was ruled out by referee Peter Bankes for a foul by Gregory on keeper Smith in the build-up, while substitute Fred Onyedinma missed the final chance of the evening in injury time.
Nottingham Forest manager Mark Warburton told BBC Radio Nottingham:
"Millwall were very good. They deserved something from the game.
"They were direct, they were effective. They won the first ball and created chances. Too many times we were loose in possession.
"To play like that and get three points, we are very relieved. We had some good points but were way below our normal level.
"Barrie McKay is a real talent. He is an outstanding player who can be anything he wants to be. He has real technical ability and class."
Millwall manager Neil Harris said:
"The ref said it was a foul from Gregory on the keeper. But I felt it was momentum. All we ask for is consistency as managers. Most people have said it is a goal, when they have seen it back. They cannot all be wrong.
"We dominated the game against a really good Forest side. The players executed the gameplan perfectly. We worked into good positions and created good chances. It was a top performance.
"You have to be clinical when you get your chances at this level. It was a good performance, but we have to be more ruthless.
"There were encouraging things to take from this. It is about how we react to this now."
