Cayetano Simplicio Arellano y Lonzón (March 2, 1847 – December 23, 1920) was the first Chief Justice of the Supreme Court of the Philippines under the American Civil Government.

He worked with the Americans under General Otis and re-established the Audiencia Territorial as the Supreme Court.

During the Spanish regime, he was appointed as a Magistrado Suplente of the Audiencia Tribunal de Manila.

Arellano, together with Pedro Paterno, Benito Legarda, Florentino Torres and Felipe Buencamino, testified before the Schurman Commission that the Philippines was not yet ready for self-rule.

Upon the onset of the American civil government in 1901, US President William McKinley appointed Arellano as the first Supreme Court Chief Justice.