Vinylester is a resin produced by the esterification of an epoxy resin with an unsaturated monocarboxylic acid. The reaction product is then dissolved in a reactive solvent, such as styrene, to a 35 - 45 percent content by weight.

It can be used as an alternative to polyester and epoxy materials in matrix or composite materials, where its characteristics, strengths, and bulk cost intermediate between polyester and epoxy. Vinyl ester has low resin viscosity (approx 200 cps), than polyester (approx 500cps) and epoxy (approx 900cps).

In homebuilt airplanes, the Glasair and Glastar kit planes made extensive use of vinylester-reinforced fiberglass structures. It is a common resin in the marine industry due to its increased corrosion resistance and ability to withstand water absorption. Vinyl ester resin is extensively used to manufacture FRP tanks and vessels as per BS5994.