"Just because I'm the top-grossing actress of all time does not mean I'm the highest paid," she told the magazine. "I've had to fight for everything that I have. It's such a fickle and political industry."
In December, Forbes named Johansson as the top-grossing actor of 2016. Last year, her films "Captain America: Civil War" and "Hail, Caesar!" brought in $1.2 billion globally, Forbes reported.
The wage gap between men and women in Hollywood has been a hot topic in recent years, and Johansson said she's felt pressure to speak out about it.
"Some people felt I should talk about my personal struggle in order to shed a spotlight on the greater issue," she told Marie Claire. "Maybe I'm being presumptuous, but I assumed it was obvious that women in all positions struggle for equality. It's always an uphill battle and fight."
That doesn't mean Johansson is against advocating for what you believe in, however, especially as a celebrity.
"[I believe] that it is really important to hear people in various positions of power to voice their opinions, their story," she said. "Why not? Why can't I have the voice? Why can't I use my platform? What's the point of having it if you don't use it? If you don't want to get involved, please, the noise is loud enough. But if you've got something to say, say it."