We demonstrate dark-state condensate formation of an ultracold quantum gas coupled into a high-finesse cavity and excited by an oscillating optical lattice. Experimentally and theoretically, we show that atoms in the dark state exhibit strong suppression of binding to cavities. In theory, this is supported by solving the dynamics of a minimal three-level model and a complete atomic cavity system. The symmetry of the condensate wavefunction is antisymmetric with respect to the potential minimum of the pump lattice and exhibits staggered signs along the cavity direction. This symmetry holds even when the dark state is decoupled from the cavity and the pump intensity is turned off.
