On Friday night, she posted a picture of her 13-year-old son Rocco boxing and used a hashtag that contained a variation of the n-word.
When fans objected, she defiantly called them haters, but in a statement to The Associated Press on Saturday she was contrite, saying: "Forgive me."
Madonna said she is not a racist and she did not mean to use the word as a slur but knows there is no way to defend its use. She said she used it as a term of endearment.
She said she apologizes if it gave the wrong impression.
Besides Rocco, Madonna has three other children, including two black children adopted from the African nation Malawi.