Polyethylene 2,5-furandicarboxylate, also named poly(ethylene 2,5-furandicarboxylate), polyethylene furanoate and poly(ethylene furanoate) and generally abbreviated as PEF, is a polymer that can be produced by polycondensation or ring-opening polymerization of 2,5-furandicarboxylic acid (FDCA) and ethylene glycol. As an aromatic polyester from ethylene glycol it is a chemical analogue of polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). PEF has been described in (patent) literature since 1951, but has gained renewed attention since the US department of energy proclaimed its building block, FDCA, as a potential bio-based replacement for purified terephthalic acid (PTA) in 2004.