GRANDMA's Window is the online presentation of the GRANDMA (Genealogical Registry and Database of Mennonite Ancestry) database produced by the California Mennonite Historical Society (CMHS). This database contains information on over a million individuals, most of whose ancestral lines can be traced to Mennonite communities in Prussia (now Poland) and South Russia (now Ukraine).

This database is available from CMHS as a CD-ROM, updated every few years; it is compatible with "Brother's Keeper" software which can generate a large variety of reports.

This online presentation contains the same data, but is updated several times a year. The GRANDMA Online site does not provide every reports available through "Brother's Keeper". However, GRANDMA Online does include some new ones including links to subscriber's historical photographs. GRANDMA's Window is enabled by subscription from CMHS.