PT1-AA1 is the Tau'ri designation for a planet in the Milky Way galaxy which held a Stargate and was visited by personnel from Stargate Command.
In 1998, after SG-1 escaped the prison Hadante with Linea, Linea used a computer in Stargate Command to look at PT1-AA1 as a probable planet for her to escape to before the SGC could discover her true identity. (SG1: "Prisoners")