4-Fluorobenzoic acid (p-fluorobenzoic acid) is an organic compound with the formula C7H5FO2.

This colourless solid is a derivative of benzoic acid carboxylic acid.

It may be prepared via the Schiemann reaction, in which a 4-aminobenzoic acid, protected as the ethyl ester, is diazotised and then fluoride introduced using tetrafluoroborate.

Hydrolysis of the ester converts it back to the free acid.

[2] 4-Fluorobenzoic acid has been observed to form by the aerobic biotransformation of 4-fluorocinnamic acid.