Perisai Tritunggal atau Scutum Fidei (Latin untuk "perisai iman") adalah sebuah simbol visual Kristen yang mengekspresikan banyak aspek dari doktrin Tritunggal, menjelaskan paruh pertama dari Kredo Athanasius dalam bentuk diagram. Di Eropa pada akhir abad pertengahan, lambang tersebut dijadikan lambang heraldik Allah (dan Tritunggal).

• "The Heraldic Imagination" by Rodney Dennys (1975). (Good historic and heraldic references)
• "An Illustrated Fragment of Peraldus's Summa of Vice: Harleian MS 3244" by Michael Evans in Journal of the Warburg and Courtauld Institutes, vol. 45 (1982), pp. 14–68. JSTOR 750966 (Contains descriptions and photos of most known surviving 13th-century diagrams, including experimental attempts to use the basic structure of the diagram for other purposes)
• "Church Symbolism: An Explanation of the more Important Symbols of the Old and New Testament, the Primitive, the Mediaeval and the Modern Church" by Frederick Roth Webber (2nd. edition, 1938). OCLC 236708 (Convenient overview from the point of view of Christian symbolism; also, the earliest attestation of the exact phrase "Shield of the Trinity" that I can find)
• "Handbook of Christian Symbolism" by William James Audsley and George Ashdown Audsley (1865). (Probably the earliest significant source for the 19th-century revival of use)