Three new pyrrolizidine alkaloids, leptanthine (2), its corresponding N-oxide 1, and N-oxide of 3′-O-acetylechihumiline (3), were isolated from the aerial parts of Onosma leptantha, together with two known alkaloids of the same type, echihumiline (5) and echihumiline N-oxide (4). Their structures and configurations were determined by chemical and spectroscopic methods, especially 1D and 2D NMR analyses, including long-range 1H, 15N correlations at natural abundance.