The Mercedes driver - who is bidding for a fifth successive race victory this weekend - beat team-mate Nico Rosberg by a slender three hundredths of a second, suggesting the pair could be in for another close fight on the Monte Carlo streets.
The Silver Arrows again appeared to enjoy a significant advantage, and will be confident of securing a sixth pole position from six races in tomorrow's qualifying session.
Red Bull's Daniel Ricciardo was best of the rest, lapping 0.235s shy of Hamilton but half a second faster than team-mate Sebastian Vettel. Fernando Alonso split the Red Bulls, beating Vettel, with Kimi Raikkonen sixth in the second Ferrari - albeit over a second shy of Hamilton's benchmark.
As ever, a number of drivers ran a foul of Monaco's notoriously tight streets, which were made all the tricker by resurfacing work which has taken place ahead of this year's race. Significantly, Sauber's Adrian Sutil lost the rear and crashed at Mirabeau, ending his session with 15 minutes remaining, while Max Chilton spun his Marussia at the same corner half an hour into the session and was unable to resume. The Briton had managed just seven laps before his error.
Free practice 1 - top-six times
- Lewis Hamilton (Mercedes) 1m18.271s
- Nico Rosberg (Mercedes) +0.032s
- Daniel Ricciardo (Red Bull) +0.235s
- Fernando Alonso (Ferrari +0.659s
- Sebastian Vettel (Red Bull) +0.772s
- Kimi Raikkonen (Ferrari) +1.196s