The B191 is a short B-road in east London. The road existed in 1922 but was unclassified; it gained its present number around 1930 when the area was still rural and in the intervening years has become part of the Becontree Estate.
The road starts on the A124 Longbridge Road and heads north along the residential Bennett's Castle Lane. Presently the road bends to the left and shortly afterwards crosses the unclassified D2 Becontree Avenue at traffic lights. The B191 continues a short distance further before ending at a T-junction on the A1083 Green Lane.