Lieuwe (Leo) van Aitzema (19 November 1600, in Dokkum, in the Province of Friesland – 23 February 1669) was a Dutch historian, diplomat, and secret agent.
He studied at the local University of Franeker and graduated from the University of Orleans in France.
In 1617, he published a volume of original poetry (in Latin), entitled Poemata Juvenilia (Poems of Youth). This rare work is preserved in the collection of the British Museum in London.
His interest was politics and for thirty years was a resident and minister for the Hanseatic towns of the Hague.
He died in the Hague, Netherlands, on 23 February 1669.
His most important work was a political and diplomatic history of the Netherlands published in 14 volumes between 1655 and 1671. These volumes contain a large number of official documents and letters. In part because of this transparency, he was considered a traitor by many in the Netherlands and remained a controversial figure.