The reigning champion from Flushing Meadows needed just 17 minutes to serve up an opening set bagel.
Stephens responded to take the second before Raducanu bounced back to emphatically close out the match, recording her eighth straight victory at a major.
Raducanu wins headline first-round encounter
Making her debut in Melbourne, Raducanu blitzed through the opening set. A pair of unforced errors by Stephens gave the Brit a 2-0 lead.
A looping winner down the line gave the 17th seed a double-break and she completed the whitewash two games later.
Consecutive double faults handed Stephens a break in the opening game of the second set. After rallying to draw even, a wayward forehand gave the American a 3-2 lead.
That was the first of four straight games won by the 2017 US Open champion, sealing the set with a blistering forehand that leveled the match at one set all.
After coming through a challenging opening game in the third set, Raducanu broke when Stephens sent a backhand long to go in front 2-0.
More attacking play paid off for the 17th seed as she forced Stephens into a forehand that hit the top of the net to extend her advantage to 4-0.
Serving for the match at 5-1, an unreturned first serve brought up three match points and after wasting the first two, a sublime drop shot on the third improved her career record in majors to 11-1.