The former world number one has birdied the final hole of her opening round to card a two-under 70 at the ANA Inspiration in California.
Ko’s playing partner Lexi Thompson is one of the three leaders at three-under par.
Lydia Ko won the ANA Inspiration in 2016 – her second and most recent major title triumph.
Meanwhile, fellow Kiwi Danny Lee has opened the PGA Tour’s Texas Open with a four-under 68.
He’s also just one shot off the clubhouse lead.