Is it ok to run a stereo amp with just one loudspeaker?

[Miller-8]

Could it cause damage?

 

[as_audio]

yes, no

 

[rayma]

Without further information, you should not do this.
Most/all tube amps, don't do this.

Many solid state amps may be ok, but there are exceptions.
If it will be run at high levels with an open circuit output, don't.
It's best to remove the signal and short the input, if the output is unused.