We present a catalogue of 233 BL Lacertae objects compiled through an extensive bibliographic search updated to mid-1995. A large fraction of the sources listed in the catalogue belongs to well-defined samples and can be used for statistical purposes. A smaller fraction consists of miscellaneous (but confirmed) BL Lacs and of objects classified as BL Lac candidates. We discuss the selection criteria of the different samples, report the discovery of two previously unnoticed BL Lacs in the Palomar-Green survey, and comment on the possible association of some of the still unidentified high galactic latitude gamma-ray (EGRET, see Thompson et al., =1995ApJS..101..259T) sources with BL Lacs. Some statistical properties of the catalogue are also briefly discussed.