The Constitution doesn’t use the exact phrase “separation of church and state,” but the principle comes mainly from the First Amendment, which says: “Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof.”

What that means

  • The government cannot create an official religion or favor one religion over another.
  • The government also cannot block people from practicing their religion freely.
  • Courts and legal scholars often describe this as a “wall of separation,” a phrase associated with Thomas Jefferson, but that phrase itself is not in the Constitution.

In plain English

This means the state is supposed to stay neutral about religion. It may not run religion, endorse religion, or coerce religious practice, but people and politicians can still express religious views in public life.

The exact text

“Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof...”

TL;DR: the Constitution protects both sides of the idea — no government- established religion, and no government interference with free exercise of religion.