Tannins are complex phenolic substances that can be extracted from many kinds of plants, especially from dicotyledonous ones, and distributed in different parts of the plant structure, depending on the species: roots, trunk, barks, seeds, fruits, and leaves at diverse concentrations. This chapter presents a selection of results showing that tannin can be an excellent precursor of carbon electrodes for supercapacitors. It deals with condensed tannins, which are characterized by aromatic rings bearing hydroxyl groups. Due to such polyphenolic structure, tannins are able to undergo the same kinds of chemical reactions as those known for resorcinol or phenol, two synthetic molecules of petrochemical origin used to prepare commercial resins. There are four types of poly-flavonoids composing condensed tannins: prorobinetinidin, prodelphinidin, profisetinidin, and procyanidin. Glucose, sucrose, furfuryl alcohol, or resorcinol, among others, have been commonly used as carbon precursors for preparing ordered mesoporous carbons (OMCs).