forefather
A male ancestor from many generations long ago.
A forefather is an ancestor from many generations ago, someone from whom you are descended but who lived long before your grandparents or even great-grandparents. Your forefathers might have lived hundreds or even thousands of years ago.
The word appears most often when talking about the people who came before us and shaped the world we live in today. Americans sometimes call the men who founded the United States the Founding Fathers or forefathers, since they established the nation's government and wrote its Constitution. When someone refers to our forefathers, they usually mean the people who built the institutions, traditions, or communities we've inherited.
The word carries a sense of respect and connection across time. Your forefathers passed down not just their genes but also their values, stories, and accomplishments. A scientist might study what her forefathers discovered. A craftsperson might use techniques their forefathers developed centuries ago. The word reminds us that we're part of a long chain of people stretching back through history.
Notice that forefather specifically refers to male ancestors, while forebears is a gender-neutral word meaning the same thing.