Observations are reported of weak emission from the ground vibrational state of SiO in the Orion molecular cloud. It is shown that this emission has a rather smooth low-intensity profile extending over a large velocity range and is present at velocities where maser emissions from the first and second vibrational states are absent. Based on this difference, the present emission is interpreted as thermal emission in the ground state in regions where there is insufficient excitation to produce the vibrationally excited masers. Possible origins are considered for the Orion SiO maser, and it is noted that only VY CMa shows a profile that could be interpreted as ground-state maser emission.