Williams had 31 winners among the 58 points she won in a dominant performance that took 56 minutes. She allowed Barty a mere six points -- two off double faults -- when Williams served.
Four seeded players, including No. 6 Petra Kvitova, were ousted as the year's first tennis major began.
Kvitova fell to No. 87-ranked Luksika Kumkhum 6-2, 1-6, 6-4. Kvitova committed 40 unforced errors, including 18 in the third set. Kumkhum won nearly half (46-of-97) of the points off Kvitova's serve.
Both members of the No. 1-ranked and defending Australian Open women's doubles team dropped singles matches Monday. Julia Goerges ousted seventh-seeded Sara Errani 6-3, 6-2 with five breaks and Zheng Jie took out No. 12-seeded Roberta Vinci 6-4, 6-3 by cashing in five of her seven break opportunities.
Alison Riske also pulled off an upset, eliminating No. 23-seeded Elena Vesnina 6-2, 6-2.
Ekaterina Makarova, the No. 22 seed, ousted Venus Williams 2-6, 6-4, 6-4. Williams was up a break in the set but wasn't able to hold on. She had 50 winners but also 56 unforced errors, with 21 coming in the third set.