Alameda County adalah county yang terletak di negara bagian California, Amerika Serikat. Jumlah penduduk berdasarkan estimasi tahun 2008 sebesar 1.474.368 jiwa.
Oakland Township – the northern portion subsequently became the cities of Berkeley and Albany.
Alameda Township – now essentially coterminous with the City of Alameda.
Brooklyn Township – mostly contained within Oakland and Piedmont.
Eden Township – partly incorporated into San Leandro and Hayward, the rest contains the communities of Castro Valley, San Lorenzo, and other unincorporated areas.