The move comes 14 months into the Middle East war sparked by the Hamas attack on Israel on 7 October 2023.
Mr Netanyahu said a “crisis of trust” had developed between him and Mr Gallant.
He said there had been too many gaps between them over the management of Israel’s wars.
The two have often been at odds over the handling of the Gaza war.
A previous attempt to fire Mr Gallant in March last year led to widespread street protests against Mr Netanyahu.
