This package is a LaTeX implementation of the business letter formatting that is used at Leiden University, using the institute graphic identity as specified on www.leidenuniv.nl. The LEIletter class is an extension of the standard KOMA-script letter class scrlttr2. It is intended to be used for writing business letters. It is compliant to the house style and allows for using windowed envelopes of the DL format, with right-aligned window. The class requires and uses the following packages that are part of most modern LaTeX distributions: graphicx, ifthen, array, babel, ragged2e, hyperref, textcase, microtype, scrlayer-scrpage, geometry, setspace, lipsum, and minionpro. The package relies on the Minion Pro fonts from Adobe, which are commercial but easily available.