Is Bleach episode 139 filler?
Canon No, episode 139 of Bleach is canon.
#139
Ichigo vs. Grimmjow, the 11-second battle!
一護VSグリムジョー、11秒の戦い
Aired 5 Sept 2007
Mochibayo compiled this list from MyAnimeList's labels, because MyAnimeList's episode data is not reaching us at the moment.