軟質或軟凝聚物是凝聚物的一個子領域，包含各種物理系統，這些物理系統由于熱波動幅度的熱應力或機械應力而變形或結構改變。它們包括液體、膠體、聚合物、泡沫、凝膠、顆粒材料、液晶和許多生物材料。這些材料具有一個重要的共同特征，即主要的物理行為發生在與室溫熱能相當的能量尺度上。在這些溫度下，量子方面通常并不重要。Pierre Gilles de Gennes被稱為“軟物質的奠基人”，在1991年獲得諾貝爾物理學獎，因為他發現研究簡單系統中有序現象的方法可以推廣到軟物質中更復雜的情況，特別是液晶和聚合物的行為。

Soft matter or soft condensed matter is a subfield of condensed matter comprising a variety of physical systems that are deformed or structurally altered by thermal or mechanical stress of the magnitude of thermal fluctuations. They include liquids, colloids, polymers, foams, gels, granular materials, liquid crystals, and a number of biological materials. These materials share an important common feature in that predominant physical behaviors occur at an energy scale comparable with room temperature thermal energy. At these temperatures, quantum aspects are generally unimportant. Pierre-Gilles de Gennes, who has been called the "founding father of soft matter," received the Nobel Prize in physics in 1991 for discovering that methods developed for studying order phenomena in simple systems can be generalized to the more complex cases found in soft matter, in particular, to the behaviors of liquid crystals and polymers.