[1] Perfluorinated compounds impact the Earth's radiative balance. Perfluorotributylamine (PFTBA) belongs to the perfluoroalkyl amine class of compounds; these have not yet been investigated as long-lived greenhouse gases (LLGHGs). Atmospheric measurements of PFTBA made in Toronto, ON, detected a mixing ratio of 0.18 parts per trillion by volume. An instantaneous radiative efficiency of 0.86?W?m^?2?ppb^?1 was calculated from its IR absorption spectra, and a lower limit of 500?years was estimated for its atmospheric lifetime. PFTBA has the highest radiative efficiency of any compound detected in the atmosphere. If the concentration in Toronto is representative of the change in global background concentration since the preindustrial period, then the radiative forcing of PFTBA is 1.5 × 10^?4?W?m^?2. We calculate the global warming potential of PFTBA over a 100?year time horizon to be 7100. Detection of PFTBA demonstrates that perfluoroalkyl amines are a class of LLGHGs worthy of future study.