Van Niekerk played the last of her 194 internationals in September 2021.
After an ankle injury in early 2022, she attempted to return for a home World Cup in February 2023 but Cricket South Africa (CSA) said she did not meet the required time for a 2km run – rules which have since been relaxed.
She said she was “absolutely broken” by that decision and retired soon after.
In a social media post on Monday, Van Niekerk said: “I sincerely apologise to Cricket South Africa and the cricket family for how I handled my retirement, and I am deeply grateful for the opportunity to hopefully one day express my skills again on the international stage.
“I know the standards of the team and the women’s game continue to rise, and I am ready to work hard to meet them.
“I return with renewed energy, focus and a deep sense of gratitude for this chance.”
South Africa have named 20 players in their World Cup training squad, though that does not include captain Laura Wolvaardt or all-rounders Chloe Tryon and Marizanne Kapp who are currently playing in The Hundred.
The overall squad must be cut to 15 for the World Cup.