The zero-field NMR of Mn55 has been observed directly in the antiferromagnetic state of MnF2. A single resonance, with linewidth ∆ν55~=1.3 Mc/sec, was observed in the frequency range of 650-675 Mc/sec and the temperature range of 1.3-20.5°K. The extrapolated Mn55 NMR frequency at 0°K is found to be ν055=671.4+/-0.2 Mc/sec. Combining the 0°K Mn55 NMR frequency together with the dipolar field Hdip=+5.770 kOe and the hyperfine coupling constant A55=-(90.78+/-0.3)×10-4 cm-1, measured for Mn2+ in ZnF2, gives a value for the zero-point spin deviation of 1-<S>S=(0.43+/-0.34)%. This value is to be compared with the value predicted by spin-wave theory of 2.37%. The observed temperature dependence of the Mn55 NMR frequency agrees, within experimental error, with the temperture dependence of the F19 zero-field NMR in antiferromagnetic MnF2. Upper and lower limits of 1300 kc/sec and 600 kc/sec are placed on the contribution to the Mn55 NMR linewidth in antiferromagnetic MnF2 by the Suhl-Nakamura interaction.