motherhouse

The convent in which the mother superior of a religious community lives.

The original convent of a religious community.

The monastery from which the other ‘houses’ of a religious order or congregation were (directly or indirectly) founded, often eponymous.

The convent which is the seat (and often the above original foundation) of the superior of an order or congregation, and/or on which lower ranking houses (such as priories under an abbot) depend.