Women and Parashat Zachor - Yechaveh Da'at 1:84

In this teshuva, Rav Yosef deals with the issue of whether or not women are obligated to hear parashat zachor read in shul. He begins by pointing out that it is a mitzva d'oraita to hear about the mitzva to wipe out Amalek. However, he notes that that does not specifically have to refer to hearing what we call parashat zachor, and in fact one can fulfill this obligation at any point during the year. That being the case, this would be a mitzvat aseh she-ein ha-zman grama, and women would be obligated just as men are.

However, there is a second side to the issue. The Sefer HaChinuch points out that women should be exempt from this mitzva since the point of remembering what Amalek did is so that we can then go out and destroy them, and the Gemara in Yevamot 65b states clearly that it is not the way of women to be involved in conquest. As such, many Acharonim followed this view and exempted women from having to hear parashat zachor. While Rav Yosef favors this view, he encourages women to hear parashat zachor anyway in order to fulfill the view that obligates them in hearing it.