
The BEL 20 is the benchmark stock market index of Euronext Brussels. In general, the index consists of a minimum of 10 and a maximum of 20 companies traded at the Brussels Stock Exchange. Since 20 June 2011, the BEL20 has contained 20 listings, with the exception a one month period in May-June 2018 when Ablynx stock was removed following the takeover by Sanofi, only to be replaced mid June by arGEN-X.

Ackermans & van Haaren is a diversified group operating in four core sectors: Marine Engineering & Contracting, Private Banking, real estate and senior care and energy and resources.

Ageas is a Belgian multinational insurance company co-headquartered in Brussels. Ageas is Belgium's largest insurer and operates in 14 countries worldwide. The company was renamed from Fortis Holding in April 2010 and consists of those insurance activities remaining after the breakup and sale of the financial services group Fortis during the financial crisis of 2007-2010.

Colruyt Group, formerly known as Etablissementen Franz Colruyt N.V. in Dutch or Établissements Franz Colruyt S.A. in French, is a Belgian family owned retail corporation that is managing the Colruyt supermarket retail stores and other subsidiaries such as OKay, Bio-Planet, DATS 24, DreamLand, DreamBaby, etc.

Groupe Bruxelles Lambert (GBL), is a Belgian holding company invested in various sectors within companies that can be considered marketleaders and in which it can play an active role as a professional shareholder over the long term.

KBC Group N.V. is a Belgian universal multi-channel bank-insurer, focusing on private clients and small and medium-sized enterprises in Belgium, Ireland, Central Europe and South-East Asia. Besides retail banking, insurance and asset management activities, KBC is active in, among other things, European debt capital markets, domestic cash equity markets and in the field of corporate banking, private banking, leasing, factoring, reinsurance, private equity and project and trade finance in Belgium, Central and Eastern Europe and elsewhere. KBC is an acronym for Kredietbank ABB Insurance CERA Bank.

The Proximus Group is a provider of digital services and communication on the Belgium and international markets. In Belgium, its main products and services are offered under the Proximus and Scarlet brands. The Group is also active in Luxembourg as Proximus Luxembourg SA, under the brand names Tango and Telindus Luxembourg, and in the Netherlands through Telindus Netherlands. The Group's international carrier activities are carried out by BICS, one of the world's leading voice carriers and the largest provider of mobile data services worldwide. Proximus Accelerators, its ecosystem of IT partners, support companies in their digital transformation.

Solvay is an international chemical company founded in 1863, with its headquarters in Neder-Over-Heembeek, Brussels, Belgium.

Telenet Group N.V. is the largest provider of cable broadband services in Belgium. Its business comprises the provision of analog and digital cable television, fixed and mobile telephone services, primarily to residential customers in Flanders and Brussels. In addition, Telenet offers services to business customers all across Belgium and in Luxembourg under its brand Telenet Solutions.

UCB is a multinational biopharmaceutical company headquartered in Brussels, Belgium. UCB is an international company with a revenue of €4.178 billion in 2016 which focuses primarily on research and development, specifically involving medications centered on epilepsy, Parkinson's, and Crohn's diseases. The company's efforts are focused on treatments for severe diseases treated by specialists, particularly in the fields of central nervous system (CNS) disorders, inflammatory disorders, and oncology.

Umicore N.V.. formerly Union Minière, is a multinational materials technology company headquartered in Brussels, Belgium.