In his opening remarks, Macron told the summit in English: "France and Europe are pragmatic and realistic. We want to develop employment, business, innovation. We believe in cooperation and multilateralism".
He warned however, in reference to the battle over 5G between the US and China, that "when it comes to 5G, we are being very careful over the access to the technologies in this network in order to preserve our national security".
He said it was "not appropriate to start a war over technology or commerce, regardless of the country."
In reaction to a question about the US decision to blacklist the Chinese telecom giant Huawei, Macron said "it is not the best way" to defend national security, nor a good way to lower tensions."
Flying cars in Paris?
On the list of highly anticipated innovations at VivaTech is flying car prototypes, which have become a regular attraction at the annual expo, created in 2016.
On Wednesday, European aerospace giant Airbus and Paris underground operator RATP announced will study the viability of adding flying vehicles to the city's urban transport network.
The firms will "explore the feasibility of urban air mobility services" in the French capital and the broader Ile de France region, they said in a statement.
"This is not science-fiction any more, it is fact," said Airbus chief executive Guillaume Faury. "Today we have all the technical tools. But they have to be integrated into everyday life without jeopardising our priority, which is safety.
"RATP is a good partner in such a project because of its knowledge of the associated needs and services."
There are at least 20 flying car projects underway, and the Uber ride-sharing company is looking into "flying taxis".
There have been several attempts around the world to develop flying cars, such as the Transition made by US firm Terrafugia and the AeroMobil, produced in Slovakia. Both have taken years and a lot of money to develop, and are yet to go on sale.
Women in the spotlight
Also present at the fair will be French companies La Poste, rail firm SNCF, Accor, Citroën, Orange, luxury group LVMH and L’Oréal.
The French regions have a series of stands to promote themselves as innovation hubs while "Pitch Zones" are set up for youngsters to sell their ideas to potential investors.
This year there will be a display area called the "Better Life Avenue", full of what organisers describe as "positive innovation" and green tech projects.
There will also be a particular focus on women, with the announcement of the winner of the EU Prize for Women Innovators award.
Among the prestigious guest speakers are NASA’s Holly Ridings, set to talk about the return to the Moon and Arizona State University’s Tanya Harrison who will discuss the exploration of Mars.