| ATIS GmbH | — | +49 241 5156630 | Aachen | Germany |
| ATP Wien Planungs GmbH | — | — | 1010 | Austria |
| AUPROTEC GmbH & Co. KG | verkauf@auprotec.com | +49 3722 4693930 | Limbach-Oberfrohna | Germany |
| AURIVOLT GmbH | — | — | Bad Oeynhausen | Germany |
| AVAG Holding SE | — | 49 821 740170 | Augsburg | Germany |
| AVANT | — | — | Southampton | United Kingdom |
| AVANTEST GmbH & Co. KG | — | — | — | |
| AVIA AG | — | — | München | Germany |
| AVISTA OIL | — | — | Uetze-Dollbergen | Germany |
| AW Augsburger Wohnbau GmbH | — | — | Augsburg | Germany |
| AWA Entsorgung GmbH | — | — | Eschweiler | Germany |
| AWISTA Starnberg KU | — | — | Gilching | Germany |
| AWU Abfallwirtschafts-Union Oberhavel GmbH | — | — | Velten | Germany |
| AWU Abfallwirtschafts-Union Oberhavel GmbH | — | — | Velten | Germany |
| AXOR | — | — | London | United Kingdom |
| Aachen-Laurensberger Rennverein e.V. | — | — | Aachen | Germany |
| Aachener Golfclub 1927 e. V. | — | — | Aachen | Germany |
| Aachener Grundvermogen | — | +49 221 772040 | Cologne | Germany |
| Aachener Parkhaus GmbH | — | +4924116885000 | Aachen | United States |
| Aachener Stadtbetrieb | — | — | Aachen | Germany |
| Abbott | — | +1 224-667-6100 | — | United States |
| Abfallwirtschaftsgesellschaft | — | — | Sachsenhagen | Germany |
| Abschleppdienst Walter | — | — | Übrigshausen | |
| Abwasserbetrieb Warendorf | — | — | — | |
| Abwasserwerk Vordereifel | — | — | Mayen | Germany |