The Pensées (Thoughts) is a collection of fragments written by the French 17th-century philosopher and mathematician Blaise Pascal. Pascal's religious conversion led him into a life of asceticism, and the Pensées was in many ways his life's work. It represented Pascal's defense of the Christian religion, and the concept of "Pascal's wager" stems from a portion of this work.

Prior to his death, Pascal was working on a Christian apologetics book which was never completed. When Pascal died in 1662, he left behind several draft notes. They were edited by others, and the notes were first published in the form of Pensées in 1670. The order with which the notes should be read was unclear, and various subsequent editions have attempted to order them by themes or by writing dates. The book was censored by the Catholic Church, with its printing forbidden by the Index Librorum Prohibitorum.

The style of the book has been described as aphoristic, or by Peter Kreeft as more like a collection of "sayings" than a book.

Pascal is sceptical of cosmological arguments for God's existence and says that when religious people present such arguments they give atheists "ground for believing that the proofs of our religion are very weak". He argues that the Bible actually cautions against these approaches. Scripture says that "God is a hidden God, and that, since the corruption of nature, He has left men in a darkness from which they can escape only through Jesus Christ, without whom all communion with God is cut off".

He writes that it is an "astounding fact" that no "canonical" writer ever offers such proofs, and that this omission makes it "worthy of attention." Pascal claims that atheists straw man Christianity. He writes, "If this religion boasted of having a clear view of God, and of possessing it open and unveiled, it would be attacking it to say that we see nothing in the world which shows it with this clearness. [...] On the contrary, it says that men are in darkness and estranged from God, that He has hidden Himself from their knowledge". Hence the atheists' arguments are not criticisms of Christianity. For Pascal, Christianity says God is found only by those "who seek Him with all their heart"; but atheists do not do this and their arguments are not related to this process.

Pascal writes that "Scepticism is true; for, after all, men before Jesus Christ did not know where they were, nor whether they were great or small. And those who have said the one or the other, knew nothing about it, and guessed without reason and by chance. They also erred always in excluding the one or the other." He considers truth to be arrived at "not only by the reason, but also by the heart, and it is in this last way that we know first principles; and reason, which has no part in it, tries in vain to impugn them". Sceptics then who only engage by means of reason "labour to no purpose".

The Pensées is the name given posthumously to fragments that Pascal had been preparing for an apology for Christianity, which was never completed. That envisioned work is often referred to as the Apology for the Christian Religion, although Pascal never used that title.

Although the Pensées appears to consist of ideas and jottings, some of which are incomplete, it is believed that Pascal had, prior to his death in 1662, already planned out the order of the book and had begun the task of cutting and pasting his draft notes into a coherent form. His task incomplete, subsequent editors have heavily disagreed on the order, if any, in which his writings should be read. Those responsible for his effects, failing to recognize the basic structure of the work, handed them over to be edited, and they were published in 1670. The first English translation was made in 1688 by John Walker. Another English translation by W. F. Trotter was published in 1931 with an introduction by T. S. Eliot.