The American great, who lost the top ranking to Angelique Kerber last year, blitzed the unseeded 19-year-old 6-4, 6-3 on Rod Laver Arena in scorching temperatures as she hunts down a seventh Melbourne Park crown.
It sets her up for a clash with Lucie Safarova from the Czech Republic, who saved nine match points before beating Belgian Yanina Wickmayer in their first round encounter.
"She is a great player, recently rated in the top 10. It really was one of the toughest first round matches I have ever played," Williams said of Bencic.
"I knew I had to be strong."
"Right now I have nothing to lose," added Williams, whose new fiance, Reddit co-founder Alexis Ohanian, was watching from the stands.
"Every match I play is for fun. It's self-motivating. I'm just happy to be playing."
Asked how she rated her form, she said: "I think it was pretty good. She's a really good player, so I think I was able to start out well.
"I made a few errors on some key points, but for the most part, I still was going for everything and I was able to close it out."
Williams, who lost last year's final to Kerber, came into the opening Grand Slam of the year with question marks over her form.
She has barely played since the US Open last September due to injury, and her build-up was set back when she was bundled out of this month's Auckland Classic in the second round.
But any doubts were quickly put to rest as she eased her way into the tournament, showing little emotion as she went about her business.
Both players held serve at the start as they probed for weaknesses, with Williams saving two break points in the third game before recovering to keep it at level pegging.
Bencic, a rising star whose 2016 was marred by injury, was making her work hard but it was the American who got the first break when the Swiss star looped a forehand long.
The advantage was short-lived, with Bencic bouncing straight back as Williams' serve let her down.
- Swiss riled -
Bencic, 19, is a former world number seven and has form against Williams, stunning her in the 2015 Toronto semi-finals in what remains the biggest win of her career.
But the composed Williams slowly got on top in Melbourne, breaking again in the 10th game as Bencic sent down a string of forehand errors.
The Swiss teen was getting frustrated, throwing her racquet to the ground as Williams broke again early in the second set.
The 35-year-old, in a black and white outfit, was in her groove and despite being broken in the seventh game and sending down a double fault on match point, was in control and eased to the finish line in 79 minutes.
Seeded two, Williams is attempting to break Steffi Graf's Open-era record of 22 Grand Slam singles titles, but has her work cut out if she is to go one better than the German great.
She could encounter either in-form Briton Johanna Konta, who won the lead-up Sydney International, or sixth seed Dominika Cibulkova in the quarter-finals.
Melbourne Park has been a happy hunting ground. She claimed her first Australian Open title way back in 2003, beating elder sister Venus in the final.
|© Provided by AFP Serena Williams of the US reacts after a point against Switzerland's Belinda Bencic during their Australian Open first round, in Melbourne, on January 17, 2017|
Wedding Plans Are the Last Thing on Serena Williams' Mind, But Tennis Star Is Totally Smitten With Fiancé Alexis Ohanian
Serena Williams isn't shopping florists, tasting wedding cakes and picking color schemes... yet.
The all-star tennis player is sweeping the Australian Open right now, and during a post-game press conference on Tuesday, Serena told reporters she's putting planning her upcoming nuptials to Alexis Ohanian on hold.
"It feels good," she shared when asked about her engagement to the Reddit co-founder. Williams added, "I really haven't thought about it too much. I wasn't going to think about it until after the tournament. I keep saying that in February I will start looking at the bigger picture of my life."
But just because wedding planning isn't her No. 1 priority at the moment, that doesn't mean Serena's fiancé isn't sticking by his ladylove's side. Ohanian was spotted cheering on Williams from the stand during one of her matches—Talk about a proud boyfriend moment.
Serena mentioned Alexis briefly during the press conference, and had nothing but wonderful things to say about the internet mogul. "He is an incredibly nice person. He really treats everyone the same, which is really cool to see," she gushed.
A rep for the professional athlete confirmed to E! News late last month that Serena and Alexis will tie the knot sometime in the near future. The pair reportedly coupled up in 2015, and Serena's family and friends are super supportive of their relationship. An insider told us, "They've never seen Serena this happy before with a man. It sounds cheesy, but it was love at first sight."
Shortly after news of their engagement broke, Serena stepped out alongside her man while rocking one massive diamond on her ring finger. She also flaunted the sparkler during a sweet date night at the start of 2017.
As for what makes their relationship work, the same source shared, "They laugh non-stop and that really fuels their relationship. They are on the same page in life and are excited to start something great with each other."
Serena Williams & Fiancé Alexis Ohanian Are Peak Relationship Goals
Serena Williams surprised us all when she announced her engagement to Reddit co-founder Alexis Ohanian. She revealed the news in December via a poem on Reddit (naturally). He’s worth around $150 million. She’s the greatest athlete in the word. Honestly, anyone would be lucky to date either of them. But alas, they have each other. And from the looks of things, they’re really happy with their choice to become an official thing.
During a post-match press conference at the Australian Open, Williams addressed her relationship for the first time since announcing her engagement. The tennis star told reporters that being engaged feels “really good.” When asked what she loves most about her new beau, she said that he's a "really nice" guy and "treats everyone the same, which is really cool to see. Really, really nice to see."
But it’s not likely that Williams has been wedding planning. She said that she hadn’t really thought about the engagement because she’s been “so focused” on competing at the Australian Open. I live for a love story that involves clear examples of women balancing their relationship and career.
And Ohanian certainly supports his soon-to-be-wife’s work. The Sun has pictures of the techie beaming from the stands and snapping pictures as Williams triumphed over Belinda Bencic.