Prayvaganzas are mass prayer meetings occasionally held in the Republic of Gilead. They allow everyone to gather together to pray and hear sermons. The term is a portmanteau of 'pray' and 'extravaganza'. Prayvaganzas are lead by a Commander. Often, they are held in celebration of marriages, which are arranged and take place in a mass wedding, with many couples being married at once.
In the book, Prayvaganzas are segregated and are either citywide events or just one for a particular municipal district. Men's events are to commemorate military victories, while women's events are for the aforementioned group weddings as they are the things according to the regime the things they are to rejoice in the most. Sometimes for the women, when young, fertile nuns are successfully converted by the regime, they come to a Prayvaganza where they watch these women go through the ceremony to become Handmaids.
In the TV episode "Seeds", the Waterfords head to a Prayvaganza chaired by Commander Pryce in which the handmaids and wives sit in rows while a ceremony takes place down below. Nick, among other Guardians, is escorted out to the main floor. Young brides, their faces covered by veils, then march onto the floor and stand opposite the men being “honored.” As Nick lifts his bride's veil, he sees a girl, Eden, who is much younger than him.