Aims. We characterised the properties of the bar hosted in lenticular galaxy NGC 4277, which is located behind the Virgo cluster. Methods. We measured the bar length and strength from the surface photometry obtained from the broad-band imaging of the Sloan Digital Sky Survey and we derived the bar pattern speed from the stellar kinematics obtained from the integral-field spectroscopy performed with the Multi Unit Spectroscopic Explorer at the Very Large Telescope. We also estimated the co-rotation radius from the circular velocity, which we constrained by correcting the stellar streaming motions for asymmetric drift, and we finally derived the bar rotation rate. Results. We found that NGC 4277 hosts a short ( R-bar = 3.2(-0.6)(+0.9) R bar kpc), weak (S-bar = 0.21 +/- 0.02), and slow ( Script capital R = 1.8(-0.3)(+0.5 )bar and its pattern speed (omega(bar) = 24.7 +/- 3.4 km s(-1) kpc(-1)) is amongst the best-constrained ones ever obtained with the Tremaine-Weinberg (TW) method with relative statistical errors of & SIM;0.2. Conclusions. NGC 4277 is the first clear-cut case of a galaxy hosting a slow stellar bar (Script capital R > 1.4 at more than a 1 sigma confidence level) measured with the model-independent TW method. A possible interaction with the neighbour galaxy NGC 4273 could have triggered the formation of such a slow bar and/or the bar could be slowed down due to the dynamical friction with a significant amount of dark matter within the bar region.