Othello is one of the first black heroes in English literature. A military general, he has risen to a position of power and influence. At the same time, however, his status as a black-skinned foreigner in Venice marks him as an outside and exposes him to some pretty overt racism, especially by his wife's father, who believes his daughter's interracial marriage can only be the result of Othello's trickery. Because the play portrays fears of miscegenation (the intermixing of races via marriage and/or sex), it's nearly impossible to talk about race in Othello without also discussing gender and sexuality.
In Othello, Shakespeare creates a hero who is not a racist stereotype. Despite this, Shakespeare ultimately allows Othello to succumb to the subtle racism that surrounds him.
Othello views his own racial identity as undesirable, and it is this lack of confidence in himself that allows Iago to persuade him that Desdemona is cheating on him.