Exclusive π0 electroproduction at a beam energy of 5.75 GeV has been measured with the Jefferson Lab CLAS spectrometer. Differential cross sections were measured at more than 1800 kinematic values in Q2, x B, t, and π, in the Q2 range from 1.0 to 4.6GeV2, -t up to 2GeV2, and x B from 0.1 to 0.58. Structure functions σ T+σ L, σ TT, and σ LT were extracted as functions of t for each of 17 combinations of Q2 and x B. The data were compared directly with two handbag-based calculations including both longitudinal and transversity generalized parton distributions (GPDs). Inclusion of only longitudinal GPDs very strongly underestimates σ T+σ L and fails to account for σ TT and σ LT, while inclusion of transversity GPDs brings the calculations into substantially better agreement with the data. There is very strong sensitivity to the relative contributions of nucleon helicity-flip and helicity nonflip processes. The results confirm that exclusive π0 electroproduction offers direct experimental access to the transversity GPDs. © 2012 American Physical Society.