Who said failure is not an option?

Answer 1

Eugene F. Kranz said it and used it in the title of his book:

Failure Is Not an Option: Mission Control from Mercury to Apollo 13 and Beyond by Gene Kranz (ISBN 0-7432-0079-9)

Answer 2

The line "Failure is not an option" was popularized by Gene Kranz, NASA Flight Director during the Apollo 13 mission. It conveys the determination and commitment required in high-stakes situations.