Members
Since its foundation, ENTSOG Member TSOs have provided wide coverage of the European gas market. In addition, ENTSOG's Articles of Association were modified in December 2010 to admit TSOs from EU countries currently derogated from the Third Energy Package, such as the Baltic States, as Associated Partners. This allowed for participation in ENTSOG activities.
In February 2011, TSOs from Third Party countries (candidates for EU accession, members of the Energy Community or EFTA) interested in following development of the network codes were also admitted to the Association as Observers.
ENTSOG was created on 1 December 2009 and is now comprised of:
44 TSO Members, 3 Associated Partners and 8 Observers.
Members
| Austria |  | Gas Connect Austria GmbH | Floridsdorfer Haupstrasse 1 1210 Vienna www.gasconnectaustria.at |
 | TAG GmbH (Trans Austria Gasleitung GmbH) | Wiedner Hauptstrasse 120-124 / 1050 Wien www.taggmbh.at | |
| Belgium |  | Fluxys Belgium S.A. | Avenue des Arts 31 1040 Bruxelles www.fluxys.com |
| Bulgaria |  | Bulgartransgaz EAD | 66. Pancho Vladigerov Blvd. Lulin 2, PO box 3 1336 Sofia www.bulgartransgaz.bg |
| Croatia |  | Plinacro | Savska 88A 1 |
| Czech Republic |  | NET4GAS, s.r.o. | Na Hřebenech II 1718/8 |
| Denmark |  | Energinet | Tonne Kjærsvej 65 Erritsø 7000 Fredericia www.energinet.dk |
| Finland |  | Gasum Oy (Gasum Corporation) | Gasum Oy |
| France |  | GRTgaz | 6 rue Raoul Nordling |
 | TERÉGA | Espace Volta 40, Avenue de l'Europe CS 20522 64010 Pau Cedex www.terega.fr | |
| Germany |  | bayernets GmbH | Poccistraße 7 |
 | Fluxys Tenp GmbH | Elisabethstrasse 11 | |
 | GASCADE Gastransport GmbH | Kölnische Straße 108 34119 Kassel www.gascade.de | |
 | Gastransport Nord GmbH | Cloppenburger Straße 363 | |
 | Gasunie Deutschland Transport Services GmbH | Pelikanplatz 5 30177 Hannover www.gasunie.de | |
 | GRTgaz Deutschland GmbH | Zimmerstraße 56 | |
 | terranets bw GmbH | Am Wallgraben 135 | |
 | Thyssengas GmbH | Emil-Moog-Platz 13 44137 Dortmund www.thyssengas.com | |
 | NEL Gastransport GmbH | Kölnische Strasse 108-112 | |
 | Nowega GmbH | Nowega GmbH | |
 | Ontras Gastransport GmbH | Maximilianallee 4 04129 Leipzig www.ontras.com | |
 | Open Grid Europe GmbH | Kallenbergstr. 5, 45141 Essen www.open-grid-europe.com | |
| Greece |  | DESFA S.A. Hellenic Gas Transmision System Operator S.A. | 357-359 Messogion Av., GR-152 31 Halandri, Attiki www.desfa.gr |
| Hungary |  | FGSZ Natural Gas Transmission Private Company Limited By Shares | Tanácsház u.5. 8600 Siófok www.fgsz.hu |
| Ireland |  | Gas Networks Ireland | Gasworks Road |
| Italy |  | Infrastrutture Trasporto Gas SpA | Via Nino Bonnet, 6/A 20154 Milano www.infrastrutturetg.it |
 | Snam Rete Gas S.p.A. | Piazza Santa Barbara 7 20097 San Donato Milanese (MI) www.snam.it | |
 | Società Gasdotti Italia S.p.A. | Via dei Salci, 25 03100 Frosinone (FR) http://www.gasdottitalia.it | |
| Lithuania |  | AB Amber Grid | AB Amber Grid Savanoriu av.28 LT-03116 Vilnius www.ambergrid.lt |
| Luxembourg |  | Creos Luxembourg S.A. | 2, Rue Thomas Edison L-2089 Strassen, |
| Netherlands |  | Gasunie Transport Services B.V. | Concourslaan 17 9727 KC Groningen www.gasunietransport services.nl |
.png){kind=logo} | BBL Company V.O.F. | Postbus 225 9700 AE Groningen Concourslaan 17 www.bblcompany.com | |
| Poland |  | Gas Transmission Operator GAZ-SYSTEM S.A. | ul. Mszczonowska 4 02-337 Warszawa www.gaz-system.pl |
| Portugal |  | REN - Gasodutos, S.A. | Estrada Nacional 116 Vila de Rei - (Bucelas) http://www.ren.pt |
| Romania |  | Transgaz S.A. | 1 Pieta Constantin I. Motas square RO - 551130 Medias www.transgaz.ro |
| Slovakia |  | eustream, a.s. | Votrubova 11, 821 09 Bratislava 26 www.eustream.sk |
| Slovenia |  | PLINOVODI d.o.o. | Cesta Ljubljanske brigade 11b 1000 Ljubljana www.plinovodi.si |
| Spain |  | ENAGAS TRANSPORTE S.A.U | Paseo de los Olmos 19 28005 Madrid www.enagas.es |
.png){kind=logo} | Regasificadora del Noroeste S.A. |
| |
| Sweden |  | Swedegas AB | Kilsgatan 4 SE-411 04 Göteborg www.swedegas.se |
United Kingdom |  | GNI(UK) | 5th floor, 6 St Andrews street, |
 | Interconnector (UK) Limited | Interconnector, 8th floor, 61 Aldwych, London, WC2B 4AE | |
 | National Grid Gas plc | 1-3 The Strand London www.nationalgrid.com | |
 | Premier Transmission Limited | First Floor The Arena Building 85 Ormeau Road, Belfast, BT7 1SH Northern Ireland www.premier-transmission.com |
Associated Partners
| Estonia |  | Elering AS | Kadaka tee 42 |
| Latvia |  | Conexus Baltic Grid | AS Conexus Baltic Grid |
| Switzerland |  | Trans Adriatic Pipeline AG | Lindenstrasse 2, |
Observers
| Albania |  | Albgaz |
Blv "Zhan Dark", Nr.3 |
| Bosnia and Herzegovina |  | BH-Gas Ltd. Sarajevo | Obala Kulina bana 8 |
| FYROM |  | GA-MA AD | Blvd. "Sv. Kliment Ohridski" 54 |
| Moldova |  | Moldovatransgaz | MD-5200, Р. Молдова |
| Norway |  | Gassco AS | PO Box 93 |
| Switzerland |  | Swissgas - Schweizerische Aktiengesellschaft für Erdgas | Grütlistrasse 44 |
 | Erdgas Ostschweiz AG |
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| Ukraine | .png){kind=spacer} | Ukrtransgaz | 9/1, Klovskiy uzviz St., |