Lewandowski, 33, had three hundred and sixty five days left on his contract with Bayern however had made transparent his need to sign up for Barca, who put him on the most sensible in their summer season want listing.
The Poland world, signed from Borussia Dortmund in 2014, scored 50 objectives throughout 46 video games ultimate season to assist Bayern win a tenth consecutive Bundesliga name, taking his total membership tally to 344.
Barcelona mentioned Lewandowski has a buyout clause of 500m euros (£425.9m) and has signed a four-year contract.
Lewandowski has joined up with the remainder of the Barcelona squad in Miami at the membership’s pre-season excursion to the US.
“After all, I’m right here, I’m more than pleased to be right here with Barcelona,” Lewandowski advised the Spanish membership’s media channel.
“The previous few days had been very lengthy days, however in spite of everything the deal is finished, so now I will be able to center of attention on a brand new bankruptcy in my existence, a brand new problem.
“I’ve at all times sought after to play in L. a. Liga and for the massive golf equipment. I'm right here to assist Barca get again to the highest and win as many titles as imaginable.”