Those who don't know history are doomed to repeat it.

The saying warns that ignorance of past events—especially the causes and consequences of political, social, or moral failures—makes individuals and societies likely to recreate the same mistakes. It frames historical knowledge as practical wisdom: patterns of human behavior, institutional incentives, and unintended consequences recur, so memory and study can function as a safeguard. Although often invoked in civic education and political debate, the line’s force comes from its aphoristic compression of a broader conservative argument associated with Burke: that reform should be informed by experience and tradition rather than undertaken as if history had nothing to teach.

Those who cannot remember the past are condemned to repeat it. (commonly credited to George Santayana)
Those who ignore history are doomed to repeat it.
Those who fail to learn from history are doomed to repeat it.