Mercedes confirmed on Thursday that a new power unit would be added to the pool of Hamilton given the damage sustained to the third system following a 46g impact as a result of a first-lap collision with Alpine's Fernando Alonso in the Belgian GP.
Hamilton's W13 has taken on a new internal combustion engine, turbocharger, MGU-H and MGU-K. As a result, Hamilton will start at the back of the grid.
Red Bull team-mates Max Verstappen and Sergio Perez will also drop down the order as a result of taking new engines for the event at Monza.
For Perez, it is his first ICE beyond the recommended three per season, so he serves a 10-place penalty, whereas Verstappen's RB18 takes on a fifth engine and so he will drop five places.
Ferrari's Carlos Sainz joins Hamilton at the back of the field as a result of a new MGU-K, energy store, and all gearbox components in terms of case and cassette, driveline and gear change and auxiliary components.
At the start of FP2, a new control electronics unit was installed in Sainz's F1-75, with the FIA then confirming a back-of-the-grid start due to him exceeding 15 grid-place penalties in relation to the power unit.
Valtteri Bottas, who has significantly exceeded his allocation, falls 15 places as his Alfa Romeo has a new ICE, turbocharger and MGU-H.
Yuki Tsunoda, who had already been handed a 10-place penalty for the number of reprimands this season, joins Hamilton and Sainz at the back of the grid.
The Japanese driver's AlphaTauri has a new ICE, turbocharger, MGU-H and MGU-K.