The choice of Israeli Gadot is accused of so-called whitewashing, ie when white actors portray non-white characters.
One of the critics is the author Morgan Jenkins, who writes on Twitter that it would be more "historically correct" with a protagonist who is "darker than a brown paper bag".
"For once, they could not have found an African actor," writes author James Hall.
Others oppose the criticism, pointing out that Cleopatra, the last ruler of the Ptolemaic dynasty, had roots in Macedonia.
At the same time, Israeli thinkers in turn accuse the critics of being anti-Semitic by not counting Jews as a people from the Middle East.
Gal Gadot's spokesman declined to comment.