Johannes a Leydis or Jan Gerbrandszoon van Leiden was a Dutch chronicler from the 15th century.
In all likelihood he came from a family of poorters (a special type of citizenship) from Leiden.
From sources we know that A Leydis was back in the monastery in Haarlem in 1495, filling the function of subprior.
His sympathies lay in particular with the family van Brederode and the Egmond Abbey.
Later on, the tendency of A Leydis to include fantastic stories in his work was criticised, with the harshest criticism coming from Janus Dousa.