The study of vibrational coupling and energy flow in bulk (bio)molecular systems using two-dimensional infrared spectroscopy, has dramatically broadened our ability to elucidate structures and their dynamic evoluton on uttrafast timescales. For molecules at surfaces, however, these insights have been lacking. In our study, vibrational coupling in a molecular monolayer is revealed by ultrafast two-dimensional vibrational spectroscopy, with interface specificity and (sub)monolayer sensitivity. This technique provides information on vibrational coupling and energy transfer at surfaces and interfaces with subpicosecond time resolution rendering it a unique tool for the investigation of both structural and dynamical surface processes in a wide variety of disciplines.