The 15-month suspension followed her positive test for Meldonium, which had been banned since the start of that year.
As worldwide media slammed the decision to have Sharapova walk the trophy on court, tournament director Craig Tiley defended the Open's stance - and the five-time grand slam champion.
Victoria Azarenka, another former champion, is also absent - because of a custody battle over her child - which left Angelique Kerber, who is playing in Sydney this week, as the only other former women's singles champion playing in the tournament. I certainly will hope that I put myself in that position'.
"We needed a former champion to come, she accepted the invite".
She said it was "incredibly special" to be back at Melbourne Park after being forced to watch the 2017 tournament from home.
With reigning champion Serena Williams missing the tournament, organisers chose Sharapova to represent the women.