伦常 (lún cháng) is a classical Chinese compound noun referring to the fundamental moral norms and social conventions that govern proper human relationships—especially those rooted in Confucian ethics, such as filial piety, respect for elders, marital fidelity, and hierarchical duties between ruler and subject, parent and child, husband and wife, elder and younger siblings, and friend and friend. The character 伦 (lún) means 'human relations' or 'order among people,' while 常 (cháng) means 'constant,' 'enduring principle,' or 'norm.' Together, they denote time-honored ethical standards considered essential to social harmony and personal virtue.

This term appears frequently in traditional texts, scholarly discourse, and formal commentary on ethics, family values, or cultural identity. Though less common in casual speech, it remains powerful in discussions about moral decline, intergenerational conflict, or cultural preservation. It carries a solemn, somewhat literary tone and is rarely used without reference to tradition, duty, or societal expectations.