Human companies

Butler Institute
In the early 21st century, this company was secretly researching techniques for transfering human consciousness into computers as a means of avoiding the hazards of climate change and social collapse around the world. (NA: Cat's Cradle: Warhead)

Fusion Corp
Located in Olympus Mons, it supplied energy for the Martian global power grid. (NA: Transit)

IMC

 * Main Article: IMC

Imogen
A German subsidiary of a Croatian conglomerate run by a group of expatriate Japanese shinjinrui from a technology park on the outskirts of Zagreb. Around the turn of the 22nd Century, it was involved in a black-book super solider project receiving illicit funding and support from factions of the global government. Before the project was destroyed by an illegal armed raid on Imogen's R&D facility in Leipzig, it had resulted in the birth of Kadiatu Lethbridge-Stewart. (NA: Imogen)

Travel-Mat

 * Main Article: T-Mat

The company responsible for the running of the global transmat freight network upon which the Earth had become critically dependant by the latter half of the 21st Century. When the transmat network was dismantled following its exploitation by Martian invaders, the company itself was either rolled up or simply restructured into STS. (DW: The Seeds of Death, NA: Transit)

STS
The company responsible for the running of the Interstitial Mass Transit System that linked all the worlds of the Sol system in the 1st half of the 22nd century prior to Dalek invasion. It most likely arose from the remnants of the Travel-Mat Corporation after that company's transmat network was dismantled.

Its central control facility was located inside Olympus Mons on Mars, and due to the critical nature of the transit system, the company's operation was overseen by a dedicated government Minister of the Union of Solar Republics. (NA: Transit)

Chief Controller

 * Main Article: Ming the Merciless
 * During the 2110s, this position was held by a woman known as Ming the Merciless by her underlings. Following the Stunnel Incident, she was elevated to Director General with full control over the contracted KGB security force and a ministerial security clearance.

Special Maintainance Crew

 * Main Article: The Floozies
 * A rag tag bunch of individuals ranging from a war veteran to an escapee from the Stop, the oldest members have worked for STS since its inception, spending over 30 years becoming, in the words of one superior "fucking invaluable".