||The Sleeping Beauty Problem concerns a perfectly rational agent who is put to sleep for two days. Depending on the toss of a fair coin, she is awakened once (Heads) or twice (Tails). However, after each waking, she is put back to sleep with a drug that erases her memories of the waking. The question which constitutes the problem is this: "When she is first awakened, what degree of belief will she have that the outcome of the coin toss is Heads?" The problem has proven exceedingly difficult to solve and attracts attention both for its intrinsic interest and because of the many connections between the correct answer to the problem and a wide variety of other philosophical topics including: the status of chance-credence and frequency-credence principles, the evidential relevance of essentially indexical information, the acceptability of conditionalization principles, the proper understanding of Dutch Book arguments, the status of indifference principles, and the proper interpretation of quantum mechanics.