Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. A novel class of fluorescent dyes based on the conformationally locked heterocyclic core of the chromophore of the fluorescent protein Kaede was discovered. Introduction of a single conformational lock at the benzylidene fragment of the Kaede chromophore resulted in an increase in the fluorescence quantum yield (FQY) by one order of magnitude and a redshift of ca. 60 nm in the emission spectrum. Imposing the second lock at the ethylene fragment of the Kaede chromophore provided a further increase in the FQY. Locked analogues demonstrated bright and redshifted emission in a broad range of solvents, which makes them good candidates for a wide spectrum of fluorescent-labeling applications. The chromophore of the fluorescent protein Kaede is known to be weakly fluorescent in solution owing to photoisomerization at the arylidene and ethylene double bonds. In this paper, two conformational locks are introduced at these double bonds, which leads to the creation of a novel class of highly fluorescent dyes; FQY = fluorescence quantum yield.