The rotational spectrum of the propargyl radical (H2CCCH) was recorded with Fourier-transform microwave (FTMW) spectrometer coupled with a pulsed discharge nozzle (PDN), Fine and hyperfine components belonging to the 1(01)-0(00), 2(02)-1(01), 2(12)-1(11), and 2(11)-1(01) rotational transitions in the B-2(1) ground vibronic state were observed. The analysis of the FTMW spectra resulted in the following ground-state molecular constants, with 3 sigma uncertainties given in parentheses. The rotational and centrifugal distortion constants are B-0=9523.6775(60) MHz, C-0=9206.8805(60) MHz, Delta(N)=3.44(63) kHz, and Delta(NK)=0.3753(28) MHz. The spin-rotation coupling constants are epsilon(aa)=-529.386(60), epsilon(bb)=-11.524(30), and epsilon(cc)=-0.520(32) MHz. The hyperfine coupling constants are a(F)=-36.323(24), T-aa=17.400(24), and T-bb=-17.220(37) MHz for the acetylenic (CH) proton, and a(F)=-54.21(11) and T-aa=-14.121(19) MHz for the methylenic (CH2) proton. The derived hyperfine coupling constants indicate comparable contributions of the allenyl (H2C=C=CH) and propargyl (H2C-C=CH) forms to the resonance structure [H-2(C) over dot-C=CH <----> H2C=C=(C) over dotH], (C) 1997 American Institute of Physics.