秘银（Mithril）是J·R·R·托尔金奇幻作品中虚构的一种金属。它的外表呈银白色，比钢铁坚固的多却很轻巧。这个名词最早出现在《魔戒》系列中，而后在1966年校订版的《哈比人历险记》中被追述。在1937年的第一版《哈比人历险记》中，比尔博得到的锁子甲衬衣被描述为“银铁”所制。

在《魔戒》中，托尔金写到只有中土的凯萨督姆（摩瑞亚）才能找到秘银，矮人们在那里开采。不过，在《未完成的故事》当中，托尔金提到努曼诺尔也出产秘银。

Mithril这个词来自于辛达林语中的两个词根——mith，意思是“灰色”，而ril的意思则是“闪烁，闪耀”。在昆雅语当中，这金属的名字是mistarille，米斯塔利尔。秘银也被叫做“真银”或“摩瑞亚银”，矮人对它取了不为外人所知的秘密称呼。

Mithril is a metal found in many fantasy worlds. It was originally introduced by the fantasy writings of J. R. R. Tolkien, being present in his Middle-earth. It resembles silver but is stronger than steel, and much lighter in weight than either. The author first wrote of it in The Lord of the Rings, and it is retrospectively mentioned in the third, revised edition of The Hobbit in 1966. In the first 1937 edition, the mail shirt given to Bilbo is described as being made of "silvered steel".