Bayern, also in the German Cup final, put on a fearsome performance ahead of Wednesday's Champions League semi-final against France's Olympique Lyon, scoring six goals in 62 minutes against relegation-threatened Hanover.
Croat Ivica Olic, winger Robben and Thomas Muller scored two apiece in just over an hour as the Bavarians struck at will with their opponents in complete disarray. The Dutchman added his third goal in stoppage time.
Bayern, bidding to become the first German team to win all three titles in the same season, now have 63 points, two ahead of Schalke 04, who had gone top earlier after their 3-1 win over Borussia Moenchengladbach with Ivan Rakitic scoring twice, including a penalty.
Bayer Leverkusen, who had Tranquillo Barnetta sent off for a second booking in the 19th minute, dropped to fourth place on 54 points after losing 2-1 to hosts VfB Stuttgart and put their Champions League participation in doubt.
Werder Bremen came from 2-1 down to crush hosts VfL Wolfsburg 4-2 and climb to third place on goal difference, level on points with Leverkusen.
"We scored the first goal and then we just played a very good game, it did not cost us a lot of energy and was great fun," Bayern coach Louis van Gaal told reporters.
"I think it was not just Robben but the whole team. We let the ball roll and that makes it hard for a team even if they are defending with 10 players."
Olic gave them a lead with a close-range header in the 22nd minute and Robben magnificently chipped goalkeeper Florian Fromlowitz to double it on the half hour.
Germany international Muller fired in a third a minute before the break as Hanover defended in numbers in a desperate attempt to avoid a demolition.
But with three goals in 17 minutes after the restart, by the same players as in the first half, Bayern did just that before Van Gaal substituted key players, including Franck Ribery, ahead of Wednesday's match against Lyon.
Robben stayed on and completed the rout with his third goal in stoppage time.
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