A logical graph is a special type of diagrammatic structure of graphical syntax developed for logic (such as those developed by Charles Sanders Peirce).

In his papers on qualitative logic, entitative graphs, and existential graphs, Peirce developed several versions of a graphical formalism, or a graph-theoretic formal language, designed to be interpreted for logic.

In the century since Peirce initiated this line of development, a variety of formal graph-theoretic structures that have branched out from what is abstractly the same formal base.

• Charles Sanders Peirce bibliography
• Conceptual graph
• Graph theory
• Propositional calculus
• Truth table
• Knowledge graph
• Venn diagram

Media related to Logical graphs at Wikimedia Commons

• Logical Graph @ Commens Dictionary of Peirce's Terms
• Existential Graphs, Jay Zeman, ed., U. of Florida. With 4 works by Peirce.
• Frithjof Dau's page of readings and links on existential graphs includes lists of: books exclusively on existential graphs; books containing existential graphs; articles; and some links and downloadables.
• The literature of C.S. Peirce’s Existential Graphs (via Internet Archive), Xin-Wen Liu, Institute of Philosophy, Chinese Academy of Social Sciences, Beijing, PRC. A whole lot there.