We report the detection of V1298 Tau b , a warm Jupiter-sized planet ( R _ { P } = 0.90 \pm 0.05 ~ { } R _ { \mathrm { Jup } } ,P = 24.1 days ) transiting a young solar analog with an estimated age of 23 million years . While hot Jupiters have been previously reported around young stars , those planets are non-transiting and near-term atmospheric characterization is not feasible . The V1298 Tau system is a compelling target for follow-up study through transmission spectroscopy and Doppler tomography owing to the transit depth ( 0.5 % ) , host star brightness ( K _ { s } = 8.1 mag ) , and rapid stellar rotation ( v \sin { i } = 23 km s ^ { -1 } ) . Although the planet is Jupiter-sized , its mass is presently unknown due to high-amplitude radial velocity jitter . Nevertheless , V1298 Tau b may help constrain formation scenarios for at least one class of warm Jupiters , providing a window into the nascent evolution of giant planet interiors and atmospheres .