Singlet fission (SF) in two or more electronically coupled organic chromophores converts a high-energy singlet exciton into two low-energy triplet excitons, which can be used to increase solar cell efficiency. Many known SF chromophores are unsuitable for device applications due to chemical instability and low triplet state energies. The results described here show that efficient SF occurs in polycrystalline thin films of 9,10-bis(phenylethynyl)anthracene (BPEA), a commercial dye that has singlet and triplet energies of 2.40 and 1.11 eV, respectively, in the solid state. BPEA crystallizes into two polymorphs with space groups C2/c and Pbcn, which undergo SF with k(SFA) = (109 +/- 4 ps)(-1) and k(SFB) = (490 +/- 10 ps)(-1), respectively. The high triplet energy and efficient SF evidenced from the 180 +/- 20% triplet yield make BPEA a promising candidate for enhancing solar cell performance.