The Bavarians, who face Real Madrid in the Champions League last eight this month, remained firmly on track for a record-extending fifth consecutive Bundesliga crown with yet another dominant performance.
Lewandowski, who joined Borussia Dortmund's Pierre-Emerick Aubameyang at the top of the scorers' list with 24, beautifully controlled a Thiago Alcantara pass with his right foot and turned to shoot Bayern ahead after 17 minutes.
Thomas Mueller, who earlier hit the woodwork twice, put the ball over the line with his knee in the 36th and Poland forward Lewandowski slotted in 10 minutes after the restart to kill off the game.
Thiago grabbed a deserved goal to make it 4-0 before Lewandowski completed his hat-trick and Mueller earned his second goal to lift Bayern to 65 points.
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"What can I say about him?" said Bayern coach Carlo Ancelotti about his prolific Polish striker. "Lewandowski did what he normally does. He scored three goals and set up another two."
"I am happy to have a forward who more or less scores in every game."
Leipzig are second on 52 after their win, Naby Keita scoring twice against Darmstadt who collapsed following the sending-off of Sandro Sirigu in the 72nd minute.
Dortmund failed to keep pace, stumbling to a 1-1 draw at Schalke 04 in the Ruhr valley derby to drop to fourth on 47, a point behind Hoffenheim, winners 3-1 at Hertha Berlin on Friday.
Aubameyang put visitors Dortmund ahead with his 24th goal of the season and celebrated by putting on a superhero mask, as he had done in past derbies.
But Schalke fought back as 20-year-old Thilo Kehrer rescued a point with a powerful low shot in the 77th minute for his first Bundesliga goal.
Schalke demanded a penalty for a hand ball in stoppage time and the team mascot caused a furore after the final whistle, racing to the referee to show him a red card over his refusal to award the spot-kick.
Werder Bremen continued their climb up the table, crushing hosts Freiburg 5-2 with a hat-trick from Dane Thomas Delaney and their fifth win in six league games lifted them to 11th on 32 points.
Hamburg SV also moved away from the relegation playoff spot after Lewis Holtby's stoppage-time goal gave them a 2-1 win over Cologne and lifted them to 13th.
Eintracht Frankfurt missed a penalty in their goalless draw against Borussia Moenchengladbach to remain in seventh place, outside the European spots.
(Reporting by Karolos Grohmann, editing by Ed Osmond and Toby Davis)
