The Fourth Degree is the highest degree of the order. It is an extension of the third degree. Members of this degree are addressed as "Sir Knight". The primary purpose of the Fourth Degree is to foster the spirit of patriotism and to encourage active Catholic Citizenship. Fewer than 18% of Knights join the Fourth Degree, which is optional; of a total 1.8 Million Knights there are over 320,000 Fourth Degree Knights in over 3,000 Assemblies. A Knight is eligible to join the Fourth Degree after six months from the date of his First Degree, providing he has completed the 2nd and 3rd degrees beforehand.
Each assembly is led by a Navigator. Other elected assembly officers include the Captain, Admiral, Pilot, Scribe, Purser, Comptroller, Sentinels and Trustees. A Friar and Color Corps Commander are appointed by the Navigator. Assembly officers are properly addressed by using the title "faithful" (e.g. Faithful Navigator). Assemblies are numbered in the order in which they chartered into the Order, and are named by the local membership.