Sakho said that he has no regrets about leaving his hometown club and that he is looking forward to his future at Anfield.
"I achieved beautiful things at Paris that I am very proud of, so I can leave raising my head high," the centre-back told L'Equipe.
"Since the start of my career, my first desire has been to go on improving and reach the objectives I set.
"My career dictated me that choice. I move on without regret. Today I am joining a great club with fantastic fans. I am very proud to have signed at Liverpool."
Sakho has been capped 14 times by France.