The Finn, four-time winner at Spa-Francorchamps, lapped the track in one minute 47.974 seconds on a hot and sweltering morning.
Australian Daniel Ricciardo carried over Red Bull’s strong form from Friday’s practice sessions to take second, 0.215 seconds behind.
Four-times world champion Sebastian Vettel was third, with Ferrari, which struggled in the uncharacteristically hot temperatures on Friday, looking more competitive ahead of qualifying.
Reigning world champion Lewis Hamilton, who took on a third fresh power unit ahead of the hour-long session, was fifth.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
The Briton is set to start Sunday’s race dead last after being hit with a cumulative 55-place grid penalty and, like Friday, spent most of the session on refining his Mercedes’ long-run pace.
Like team-mate Nico Rosberg, who was seventh, Hamilton went out for a final blast on the fastest super-soft tyres in the dying minutes of the session.
Dutchman Max Verstappen, for whom this race is the closest he has to a home event, was only able to drive two laps in front of his legions of orange-clad supporters without setting a time.
The 18-year-old, who ended Friday’s opening day of practice on top of the timsheets, was sidelined with problems with his Red Bull’s gearbox, with the team investigating the issues.
Hamilton heads into the weekend gunning to become only the third driver ever to take 50 career wins.
The triple champion has won six of the last seven races, four of those in succession, and leads Rosberg by 19 points in the standings.
(Editing by Amlan Chakraborty)
