---
author:
- 'L. Chiappetti'
- 'S. Fotopoulou'
- 'C. Lidman'
- 'L. Faccioli'
- 'F. Pacaud'
- 'A. Elyiv'
- 'S. Paltani'
- 'M. Pierre'
- 'M. Plionis'
- 'C. Adami'
- 'S. Alis'
- 'B. Altieri'
- 'I. Baldry'
- 'M. Bolzonella'
- 'A. Bongiorno'
- 'M. Brown'
- 'S. Driver'
- 'E. Elmer'
- 'P. Franzetti'
- 'M. Grootes'
- 'V. Guglielmo'
- 'A. Iovino'
- 'E. Koulouridis'
- 'J.P. Lefèvre'
- 'J. Liske'
- 'S. Maurogordato'
- 'O. Melnyk'
- 'M. Owers'
- 'B. Poggianti'
- 'M. Polletta'
- 'E. Pompei'
- 'T. Ponman'
- 'A. Robotham'
- 'T. Sadibekova'
- 'R. Tuffs'
- 'I. Valtchanov'
- 'C. Vignali'
- 'G. Wagner'
bibliography:
- 'papercat.bib'
date: 'Received ; accepted '
title: 'The XXL Survey: XXVII. The `3XLSS` point source catalogue. [^1] [^2]'
---

Introduction\[SecIntro\]
========================

The XXL Survey is an X-ray survey carried out by the XMM-Newton satellite, covering two 25 deg$^2$ areas called XXL-N and XXL-S, complemented by observations at multiple wavelengths. Initial results from the survey were published in a dedicated issue of Astronomy & Astrophysics (volume 592). For the scientific motivations of the survey, the characteristics of the observing programme, and the multiwavelength 