Controlled synthesis of well-defined planar Au nanodendrites with a symmetric single-crystalline structure consisting of trunks and side branches grown along the 211 directions was realized by reducing chloroauric acid in aqueous mixed solutions of dodecyltrimethylammonium bromide (DTAB) and beta-cyclodextrin (beta-CD). It has been revealed that the formation of the supramolecular complexes of DTAB with beta-CD due to host-guest interaction is indispensable for the fabrication of these unique planar Au nanodendrites, and a proper CD-to-DTAB molar ratio is essential to their exclusive formation. A variety of Au nanostructures, such as branched particles consisting of rodlike branches and flowerlike particles consisting of platelike petals, could be readily obtained by simply changing the CD-to-DTAB molar ratio. Moreover, the obtained Au nanodendrites exhibited both a good electrocatalytic activity toward the oxidation of methanol and a good surface-enhanced Raman scattering (SERS) sensitivity for detecting p-aminothiophenol (PATP) molecules, indicating their potential applications including catalysis, biosensing, and nanodevices.