Bayern's superstar striker has not played since Poland's 3-0 World Cup qualifying win over Andorra on March 28.
But after nearly a month out, the club confirmed on Wednesday Lewandowski "completed the majority of full training", with coach Hansi Flick optimistic he could feature at Mainz on Saturday.
Bayern also had Serge Gnabry, returning from coronavirus, and Corentin Tolisso, out since February with a thigh injury, back in light training.
The defending Bundesliga champions can clinch another title this weekend and would be delighted to welcome back Lewandowski.
Despite missing several weeks, the 32-year-old still leads all players in Europe's 'top five' leagues in goals (42) and goal involvements (50) in all competitions.
Lewandowski has scored with 28.8 per cent of his shots across 36 matches, although he has also missed 25 Opta-defined 'big chances'. Only Duvan Zapata (29) and Cristiano Ronaldo (27) have squandered more, though this is likely down to the sheer number of chances that come their way.
Of his goals, 35 have come in the Bundesliga, putting Lewandowski just five shy of Gerd Muller's 1971-72 record of 40, albeit now with only four games remaining.
The domestic competition will be Lewandowski's sole focus after Bayern exited the Champions League to Paris Saint-Germain on away goals in his absence.
Lewandowski was badly missed as Bayern scored just three goals from 45 shots and eight 'big chances' over the two legs. In the 3-2 home defeat, their 31 attempts were worth 3.8 expected goals, meaning they should have netted roughly twice as many they did.
Not since Galatasaray lost 4-1 to Arsenal in December 2014 despite 32 efforts had a team been beaten while attempting 30 shots or more in a Champions League game that did not go to extra time.
Back-up Eric Maxim Choupo-Moting scored home and away against his former club, however, and had four goals in six games while Lewandowski was out.
Only Gerard Moreno (six), Kylian Mbappe and Memphis Depay (both five) in the 'top five' leagues netted more in all competitions over this period.
Julian Nagelsmann's side are just a point clear at the Bundesliga summit after three successive 1-1 draws, but they ended their winless run with a dominant showing at MEWA Arena on Wednesday.
Manchester City loanee Joao Cancelo assisted Choupo-Moting's opener just 17 minutes into his debut, before the striker teed up Leroy Sane on the stroke of half-time after Jamal Musiala's 30th-minute strike.
Substitute Alphonso Davies sealed the victory in the second half prior to Alexander Hack being dismissed late on, as Bayern picked up a first win of 2023 to remain on course for a first DFB-Pokal triumph since 2020.
Mainz did not heed the early warning signs against a dominant Bayern and were punished as Choupo-Moting expertly volleyed Cancelo's right-wing centre past Finn Dahmen at the far post.
Musiala doubled the visitors' advantage with a pinpoint left-footed finish into the bottom-right corner after Thomas Muller's delicate pass.
Joshua Kimmich then curled a free-kick from a tight angle against the left post, before Sane calmly finished from Choupo-Moting's throughball as a rampant Bayern ran riot in the first half.
Hack cleared Muller's deflected attempt off the line after the interval, while Anthony Caci whipped a rare Mainz chance narrowly wide at the other end.
Davies nodded Kimmich's right-wing cross past Dahmen for Bayern's fourth, before Hack was shown a second yellow card for a needless foul on Musiala as Bayern eased to victory.
Handed his Bayern bow as the European champions’ international stars sat out the DFB-Pokal first-round tie with Duren, Choupo-Moting scored twice in a 3-0 win on Thursday and earned the penalty for Muller to net the other goal.
The striker, who played for Paris Saint-Germain against Bayern in last season's Champions League final, signed for the treble winners on transfer deadline day.
Muller has already been impressed by his impact on and off the pitch, telling SPORT1: "[Choupo-Moting] brings the wit, he also makes jokes off the pitch.
"He fits in well with our style of play because he is also technically good with the ball. If he maintains this strike rate, he'll fit."
Choupo-Moting served as support to Kylian Mbappe, Neymar, Mauro Icardi and Edinson Cavani at PSG.
Bayern do not quite have the same wealth of striking options, but the 31-year-old still finds himself behind Lewandowski, Europe's leading scorer last season.
Choupo-Moting is happy enough with that role, though, explaining: "I have huge respect for Lewy, who was deservedly voted the best striker of last season.
"If I get my minutes after him, that's okay, and if we play together, then all the better. I'll try to play as much as possible."
Of his debut, Choupo-Moting added: "We did well and I'm happy that we won the game and that I was able to score my first goals for Bayern.
"I feel 100 per cent Bayern Munich. I hope that there will be a little more power over time - that's what I work on in training and I'm up for it."
