Dennis’ departure is seismic move in the context of modern F1, in which he has been a central figure since 1981.
Dennis joined McLaren in 1980 and took full control in 1981, after which he led the team to several periods of domination and turned it into the most successful outfit in history after Ferrari.
Under Dennis’ leadership, McLaren won 10 drivers’ titles with Niki Lauda, Alain Prost, Ayrton Senna, Mika Hakkinen and Lewis Hamilton, and seven constructors’ championships.
However, the team has slipped from the front in recent years and the decision to join forces with engine partner Honda led in 2015 to the worst season in their history.
Honda entered F1 when it was not ready, a decision at least partly down to McLaren, whose engine partnership with Mercedes was ending in 2014 and who pushed for the Honda deal to start as soon as possible.
Dennis has also failed to secure a new title sponsor to replace mobile phone giant Vodafone, which left at the end of 2013.
Other lost sponsors have been replaced by similar deals but, notwithstanding Honda’s significant financial contribution over and above the provision of free power units, the absence of a title sponsor for the past three years has cast doubt in Dennis’s fellow shareholders’ minds on his ability to procure major sponsorship contracts in the digital age.
American Zak Brown, a leading commercial figure in F1, remains the most likely candidate to replace him.
The 44-year-old’s links with McLaren were revealed by BBC Sport last month and he has moved closer to accepting a leadership position at McLaren since then.
However, Brown has also been linked with a role with new F1 owners Liberty Media, heading up their commercial operation once they complete their takeover of the F1 Group next year.
Sources close to Brown say he is more likely at this stage to accept the McLaren offer but has not made a final decision.
Dennis’ departure also raises questions about the future of McLaren Racing chief executive officer Jost Capito.
The German, the former boss of Volkswagen Motorsport, was appointed in January but only started work in September. He is strongly linked to Dennis, raising questions about his position once Dennis leaves the company.