Mechanically stabilized earth (MSE or reinforced soil) is soil constructed with artificial reinforcing. It can be used for retaining walls, bridge abutments, seawalls, and dikes. Although the basic principles of MSE have been used throughout history, MSE was developed in its current form in the 1960s. The reinforcing elements used can vary but include steel and geosynthetics.

MSE is the term usually used in the US to distinguish it from the trade name "Reinforced Earth". Elsewhere "reinforced soil" is the generally accepted term.