Yat Ahk I[1] was the third king of Mayan city-state Piedras Negras in Guatemala.

[2] The first mention of Yat Ahk I comes in the inscriptions of Yaxchilan when one of his sublords is captured by Knot-eye Jaguar I.

[3] However, it is likely that Piedras Negras had gained some degree of ascendancy over Yaxchilan.

His successor was Piedras Negras Ruler C. He could be his son.

The eleventh and final ajaw of Piedras Negras, K'inich Yat Ahk II, appears to have taken his name in memory of Yat Ahk I.