Loess (, , , or ; from German Löss ) is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. It covers about 10% of the Earth's surface.

LOESS and LOWESS (locally weighted scatterplot smoothing) are two strongly related non-parametric regression methods that combine multiple regression models in a k-nearest-neighbor-based meta-model. "LOESS" is a later generalization of LOWESS; although it is not a true initialism, it may be understood as standing for "LOcal regrESSion".