During Tuesday’s game, the Lakers player called Bennie Adams a “faggot” when the referee judged he had committed a foul.
His outburst was captured on camera. Afterwards, the star blamed “frustration in the heat of the game”.
“What I said last night should not be taken literally,” he said.
Gay rights groups were appalled and said that the remark, from one of sport’s highest-paid stars, would increase homophobia.
Last night, Human Rights Campaign president Joe Solmonese said Bryant had apologised to him in a conversation.
Mr Solmonese said: “We had a very sincere conversation in which he expressed his heartfelt regret for the hurt that his words caused. He told me that it’s never ok to degrade or tease, and that he understands how his words could unfortunately give the wrong impression that this is appropriate conduct.
“At the end of a difficult day, I applaud Kobe for coming forward and taking responsibility for his actions.”
NBA commissioner David Stern said in a statement that Bryant’s comment was “offensive and inexcusable”.
“While I’m fully aware that basketball is an emotional game, such a distasteful term should never be tolerated. Accordingly, I have fined Kobe $100,000.”
Speaking to Mason & Ireland on radio show 710 ESPN yesterday, the player said he would appeal the fine.