Coco Gauff says she feels like "we're almost going backwards" after the US Supreme Court's decision to remove the constitutional right to abortion.
On Friday, the court overturned a 1973 ruling - known as 'Roe v Wade' - that women were entitled to an abortion during the first three months of their pregnancy.
The judgement paves the way for individual US states to ban abortion.
US President Joe Biden described the decision as "a tragic error".
Biden urged states to enact laws to allow the procedure, but others such as Governor of Mississippi Tate Reeves welcomed the ruling, saying "one of the greatest injustices in the history of our country" had been overcome.
American Gauff, 18, encouraged people to continue to use their voice to ask for change and not be discouraged.
"I'm obviously disappointed about the decision made," said Gauff.
"I feel bad for future women and women now, but I also feel bad for those who protested for this, I don't even know how many years ago, but protested for this, are alive to see that decision be reversed.
"I just think that history is repeating itself - at least from my reading, researching, because I do like history, I feel like just having this decision reversed, we're almost going backwards."
The world number 12 has previously used her platform to appeal for an end to gun violence in the US and rallied for racial and social justice.
Gauff said Friday's decision "puts a lead-way into maybe reversing other things that we worked - I wouldn't say me personally - but people in the past worked so hard to reverse".
"But I still want to encourage people to use their voice and not feel too discouraged about this because we can definitely make a change, and hopefully change will happen," she added.