Timberlake and Biel broke-up in March after four years together, and the pop star told Vanity Fair magazine she remains the most 'significant' person he has loved.
'I would rather not talk about her, because it's hurtful for me,' Timberlake, 30, said. 'I do not want to say much more on it, because I have to protect things which are dear to me - for instance her.
'She is single-handedly the most significant person in my life. In my 30 years, she is the most special person, OK? So I have to protect it.'
Timberlake, who has now made a string of movies, also hinted in the article that he may be ready to quit the music world for good.
'I could see myself only doing one more big tour,' he said.