According to the United States Census Bureau, the town has a total area of 17.9 square miles (46 km²), of which 17.6 square miles (46 km²) is land and 0.3 square miles (0.78 km²) (1.79%) is water. Russell borders Granville to the south, Blandford to the west, Huntington to the north, Montgomery to the northeast and Westfield to the southeast.

The town has two very different sections: South Quarter is mainly uplands at elevations from 1,000 ft (300 m) to 1,400 ft (430 m) along the rim of a plateau west of the Connecticut River Valley.

Most of the escarpment is inside the town. This is the edge of a rift valley originating in the Mesozoic Era when Europe and North America separated. The Connecticut River still follows this rift valley, known as Pioneer Valley, for its early settlement by English Puritans. The escarpment between South Quarter uplands and the valley is forested—too steep to farm—and dissected by streams that have eroded ravines back into the uplands.

The rest of the town is a deep valley along the swift Westfield River. During the Epoch, continental glaciers scraped away soil and steepened cliffs on hills around this valley, particularly on Mounts Tekoa and Shatterack east of the river, and on Turtle Mountain standing in the middle of the valley. Although none of these peaks actually rises much above the surrounding plateau, their precipitous slopes make them appear impressively high from the valley.

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