The ground state pure rotational spectrum of silacyclobutane (SCB) (c-SiH(2)C(3)H(6)) has been investigated using both Fourier transform microwave (FTMW) and chirped pulse Fourier transform microwave (cp-FTMW) spectroscopies. Spectra of the (13)C, (29)Si, and (30)Si singly substituted isotopologues, in natural abundance, were recorded in the 6-24 GHz region along with those of the normal species. The ring inversion tunnelling splitting in the ground vibrational state was resolved and analyzed to determine the energy splitting of the two states: 75.7260(19) MHz. Structural analysis based on heavy atom substitution provided accurate geometric parameters including the bond lengths, bond angles, and ring puckering angle of the SCB ring backbone.