It is located roughly halfway between Weston-super-Mare and Bridgwater, 2.5 miles (4.0 km) from the Bristol Channel coast at Burnham-on-Sea.

The hill's size and isolated position on the levels mean that it dominates the landscape and can be seen for many miles, and its prominence is emphasised to travellers because the Bristol to Taunton railway line, M5 motorway, A370 and A38 roads all pass within a mile or less from its base.

[3][5] An isolated hill, Brent Knoll is an example of denudation – waters of the Bristol Channel eroded surrounding features leaving just the Blue Lias rocks from the Jurassic period capped with Midford Sands of the Bridport Formation.

[7] Before the Somerset Levels were drained, Brent Knoll was an island, known as the Isle (or Mount) of Frogs (Mons Ranarum), that provided a safe haven from the water and marshes.

[8] According to legend, Ider son of Nuth, who was one of King Arthur's knights, came to the Mount of Frogs on a quest to slay three giants who lived there.