贤者之石（Philosopher's stone）是一种存在于传说或神话中的物质，其形态可能为石头（固体）、粉末或液体。它被认为能拿来将一般的非贵重金属变成黄金，或制造能让人长生不老的万能药，又或者医治百病。其他的称号还有哲学家之石、天上的石头、红药液、第五元素等等。由于炼金术师们对这种物质的不懈追求，它也被赋予了大奇迹、伟大的创造等称号。有时候，这些称号也同时用来称呼那些贤者之石的制造者，以此来形象地表现他们居于炼金术的顶点。

法国炼金术士尼古拉·弗拉梅尔对贤者之石的研究使他闻名于世。

The philosopher's stone, or stone of the philosophers (Latin:lapis philosophorum) is a legendary alchemical substance capable of turning base metals such as mercury into gold (chrysopoeia, from the Greek χρυσός khrusos, "gold," and ποιεῖν poiēin, "to make") or silver. It is also able to extend one's life and called the elixir of life, useful for rejuvenation and for achieving immortality; for many centuries, it was the most sought-after goal in alchemy. The philosopher's stone was the central symbol of the mystical terminology of alchemy, symbolizing perfection at its finest, enlightenment, and heavenly bliss. Efforts to discover the philosopher's stone were known as the Magnum Opus ("Great Work").