Which amendment of the U.S. Constitution ensures no state shall abridge the privileges or immunities of citizens?

The amendment that ensures no state shall abridge the privileges or immunities of citizens is the Fourteenth Amendment. This amendment, ratified in 1868, contains several important provisions, including the Equal Protection Clause and the Due Process Clause. The specific provision you are referring to is found in Section 1 of the Fourteenth Amendment, which states that no state shall make or enforce any law that shall abridge the privileges or immunities of citizens of the United States.

This amendment is significant in protecting individuals' rights from being infringed upon by state governments, thus providing a federal standard for individual rights. It has been the basis for numerous landmark Supreme Court decisions that further defined civil rights and liberties in America. By incorporating the Bill of Rights to apply at the state level, the Fourteenth Amendment plays a crucial role in the legal framework that safeguards citizens against state violations of their constitutional rights.