IEC 61076-2-101:2012 describes M12 circular connectors typically used for industrial process measurement and control. These connectors consist of fixed and free connectors either rewireable or non-rewireable, with screw-locking. The connectors with glass to metal seal are fixed connectors only which consist of fixed glass to metal sealed styles with rewireable male contacts and are intermateable with corresponding free connectors according to this International Standard. Male connectors have round contacts 0,6 mm, 0,76 mm, 0,8 mm and 1,0 mm. The different codings prevent the mating of these coded male or female connectors to any other interfaces and cross-mating between the different codings. This third edition cancels and replaces the second edition published in 2008 and its corrigendum published in 2010. It constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: - The drawings of some styles have been corrected, - A new style with maximum 17 poles, with A-coding, has been added, as new applications for the industrial process measurement and control require a high number of poles in M12 circular connectors. The existing styles and dimensions which were specified in IEC 61076-2-101 Ed.2 are further applicable for the added interface dimension of the 17 poles versions, - Removal of the type designation and ordering information, former Tables 6 and 7 have been updated accordingly and - Inclusion of the technical content of IEC PAS 61076-2-108, which will be withdrawn after publication of this International Standard. The drawings have been updated and correction to the title of Figure 9 was made. Keywords: M12 connectors, Circular connector