San Ramon is adjacent to Danville, California, to the north and Dublin, California, to the south. Unincorporated county lands border San Ramon to the east and west. It is located around 500 feet (150 m) above sea level. Mount Diablo flanks the city to the northeast and is prominently visible from almost all parts of the city. The Las Trampas Regional Wilderness borders San Ramon's extreme northwest, at the northern end of Bollinger Canyon. The smaller Bishop Ranch Regional Preserve straddles San Ramon's western border, located approximately between Interstate 680 and the Alameda County line.
The topography of San Ramon is varied, featuring a mix of the rolling hills of the Diablo Range and the flatter basin of the San Ramon Valley. The city is predominantly urban and residential with many new housing developments, however much of the land around the city's perimeter regions remains undeveloped, and is covered by grasslands and oak tree orchards. During the drier months the grasses are golden; with the precipitation of winter and spring, the grasses turn green, in the late; fall and beginning of winter, some trees with all the leaves all fall off and die, and in the late winter and beginning of spring the leaves start growing.