泥岩（英语：mudstone）是一种沉积岩，成分比较复杂，层理不明显，由细颗粒的沉积物形成，黑色泥岩中常含有有机物质，是一种生油的岩系。泥岩根据其中混入的物质，可以分为：

• 钙质粉砂泥岩
• 铁质泥岩
• 炭质泥岩
• 水云母泥岩 等

Lutite is old terminology, which is not widely used, by Earth scientists in field descriptions for fine-grained, sedimentary rocks, which are composed of silt-size sediment, clay-size sediment, or a mixture of both. When mixed with water lutites often disintegrate into mud. Because this is a field term, there is a lack of any precise definition for it based upon specific grain-size characteristics. Lutites include a variety of fine-grained sedimentary rocks, including calcisiltite, calcilutite, claystone, mudstone, shale, and siltstone. It is equivalent to the term mudstone and the Greek-derived term pelite. Lutite was first used in 1904 by Grabau, who derived it from the Latin word for mud. He also proposed a number of prefixes to be used with and attached to "lutite" in order to designated various types of lutites. None of these prefixes are used by Earth scientists.