 People pray for all kinds of reasons. Sometimes people pray in order to give thanks, sometimes to offer praise and adoration, sometimes to apologize and seek forgiveness, and sometimes to ask for things. The focus of this article is petitionary prayer, in which a petitioner requests something. Historically, the philosophical puzzles concerning petitionary prayer that have received most attention have arisen in connection with the traditional monotheism shared by Judaism, Christianity, and Islam. According to traditional monotheism, God knows everything that can be known, is perfectly good, impassible (unable to be affected by an outside source), immutable (unchanging), and free. God is also able to do anything compatible with the possession of the qualities just enumerated. In this entry, we will explore the most prominent philosophical puzzles that arise in connection with the idea of offering petitionary prayers to God, as understood along the lines just described, along with the most influential attempts to solve them.