Bassino, who won joint gold in the parallel slalom at the last worlds in Cortina d'Ampezzo in 2021, timed 1min 28.06sec down the Roc de Fer piste in Meribel.
"It was just wonderful, in perfect conditions," said Bassino, who becomes just the second Italian female racer to win world super-G gold after Isolde Kostner in 1996 and 1997.
"Today really means a lot because it's my first super-G victory. I was really confident because I really like the slope."
Shiffrin made up for skiing out of the alpine combined on the cusp of bagging gold with a second-placed finish just 0.11 seconds behind. The silver was no real surprise as Shiffrin won the downhill at last season's World Cup Finals on the same slope.
Bronze was shared by Austria's Cornelia Huetter and Kajsa Vickhoff Lie of Norway, both at 0.33sec.
It is often said that alpine ski racing is a sport of small margins and so it proved in the French resort on a piste bathed in largely sunnny, cold conditions.
Bassino, with bib number eight, set the pace and could only look on as a raft of rivals, and podium favourites, took to the startgate.
A familiar pattern to the timings emerged: fast starting, the racers crucially lost time heading into the shady technical midsection of the course, leaving themselves too much to do in the bottom third to reel back in those invaluable hundredths of seconds.
Reigning world and Olympic champion Lara Gut-Behrami was one such racer, the Swiss eventually finishing sixth, at 0.37sec, just one-hundredth behind Ragnhild Mowinckel, the Norwegian who heads up the World Cup super-G standings paying the price for clipping a gate.
Late charger Alice Robinson of New Zealand, starting 30th, threatened to derail the podium, but faded at the bottom after leading all the way down, coming in eighth, with newly-crowned combined champion Federica Brignone of Italy in ninth.
The top 14 racers all finished within a second of Bassino and included teammate and two-time Olympic downhill medallist Sofia Goggia and two-time former downhill champion Ilka Stuhec of Slovenia.