Inter's Romelu Lukaku became the first Belgian to reach the 50-goal plateau when he opened the floodgates in the 28th minute. Following a period of unrelenting pressure from the hosts, the Red Devils swiftly forged a six-goal halftime buffer en route to a 9-0 victory.
Lukaku was the beneficiary of a nicely weighted pass from Youri Tielemans before making a series of stepovers to afford himself the space to fire home a close-range, right-footed effort.
Lukaku, Tielemans, and Toby Alderweireld all added to the one-sided score as Roberto Martinez's charges carried a 6-0 lead into the break.
Second-half substitute Christian Benteke bagged Belgium's seventh in the 79th minute, his first tally for his country since March 2017. Yari Verschaeren opened his Red Devils account from the penalty spot five minutes later. Timothy Castagne added a ninth in the 90th minute for good measure.
Belgium managed 13 shots on target to San Marino's zero. Thibaut Courtois kept a clean sheet nine days after leaving Real Madrid's Champions League stalemate against Club Brugge at the half with gastrointestinal issues.
The Red Devils are now off to their second straight European Championships after missing three continental tournaments on the spin. Russia has a stranglehold on Group I's second automatic qualifier thanks to 4-0 win over Scotland at Moscow's Luzhniki Stadium on Thursday.