Julia Gillard
When asked in 2010 on the ABC's Jon Faine program, "Do you believe in God?", Gillard answered, "No, I don't Jon, I'm not a religious person ... I'm, of course, a great respecter of religious beliefs but they're not my beliefs". Newly appointed Prime Ministers must take an affirmation of office, or swear an oath of office on the Bible.  Gillard chose an affirmation.