Star wing Ange Capuozzo was amongst the try scorers, with Lorenzo Cannone, Paolo Garbisi, Dino Lamb, Epalahame Faiva, Manuel Zuliani and Paolo Odogwu also dotting down, while Gerswin Mouton replied for Namibia.
Full-back Tommaso Allan contributed 17 points with the boot in a faultless display.
It was a 23rd straight defeat in as many World Cup matches for the African side.
Coming away with a maximum five-point haul was crucial for Italy, with clashes against pool heavyweights France and New Zealand to come.
Kieran Crowley's team is looking to make the knock-out stages for the first time.
Namibia's South African coach Allister Coetzee spoke before the match about his belief that the African nation could finally end its wait for a first World Cup victory.
![Italy vs Nambia match stats Italy vs Nambia match stats](https://livesport-ott-images.ssl.cdn.cra.cz/r900xfq60/29daf7d9-9c4c-4c6f-b7e4-6aff6dc050b7.jpg)
And they started on the front foot with fly-half Tiaan Swanepoel kicking the first points of the game.
But those hopes quickly unravelled as Italy hit straight back with a penalty of their own from Allan.
And after Namibian hooker Torsten van Jaarsveld was sin-binned for cynically dragging down a rolling maul, Italy cut loose.
The Europeans' No.8 Cannone barged over from a short-range catch-and-drive and then fly-half Garbisi ghosted through a gaping hole in the Namibian defence to dot down under the posts after a wretched line-out throw by the Africans' No.8 Richard Hardwick - deputising for the binned Van Jaarsveld - put his side in trouble.
The 14 men soon hit back, though, as Mouton was released in space out wide to dive over in the corner.
After that frenetic start in searing heat at the sun-drenched Stade Geoffroy Guichard, the pace of the game slowed markedly and neither side could add to their score before the break, with Italy turning around 17-8 ahead.
The second half was one-way traffic as Italy started it in much the same way as the first, Lamb barging over from close range after a series of pick-and-gos.
The Six Nations' perennial wooden spoon finishers then cut loose as Capuozzo showed off his talent, playing a one-two with Monty Ioane before diving over in the corner.
Replacement prop Marco Riccioni thought he had added another try but it was chalked off for a knock-on in the build-up.
However, fellow substitutes Faiva, Zuliani and Odogwu exploited a tiring Namibian defence to add a late flourish.