Ngog, 20, was a second half substitute for scorer of the first goal Fernando Torres and slotted his fourth goal in a Reds shirt past United goalkeeper Edwin van der Sar six minutes into injury time.
After the game the French forward told the club’s official web site, “This was a fantastic moment for me and the team and I would say it’s my best moment in football.
“I have always dreamed of scoring a goal for Liverpool against Manchester United and now it has happened and it is a really good feeling.
“I dedicate this goal to my family who always support me and the Liverpool supporters. We know how much this victory means to our supporters.
“I also give thanks to my teammates and the manager for always showing faith in me.
“We know we have a lot of quality so this result means everything for the team. We have worked really hard together and I think we deserved to win.”