McLaren have revealed the MCL33 car they hope will propel them back to the front of Formula 1 in 2018.
The new McLaren-Renault ran for the first time during a filming day for the team in Spain on Friday.
Asked to give a message to the McLaren fans after his first run in the MCL33, Alonso said: "The good times are coming!"
The Spaniard added: "It felt great. It's always a special moment to drive the car for the first time. Everything felt good."
As expected, the MCL33 features a striking new livery, with the McLaren colour scheme reverting to the papaya orange of the team's early years. There is also a splash of blue at the rear and on the front wing.
But of more significance when the car hits the track will be its new Renault engine with the fallen superpowers under massive pressure to deliver a vast upgrade in performance in 2018 following their split from Honda.
"If we're able to develop the key strengths of last year's chassis and marry it to an improved Renault power unit, then I think we'll be able to take a step forwards," said driver Fernando Alonso.
"Looking at our new car, I feel incredibly excited - but also apprehensive. I know just how important this car is to the team, and I just hope that it delivers in the way we all want it to."
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As expected, the new McLaren is an evolution of its predecessor.
'Much of the work on the MCL33 has been around optimising the packaging of the new Renault engine, and the incorporation of the new halo device,' the team confirmed.
On Twitter, Sky F1 analyst Mark Hughes wrote: "Of all the '18 cars so far, the new McLaren is the least visibly changed from its predecessor."
The 20-time F1 world champions haven't won a race in the sport since 2012 - Lewis Hamilton's final year with the team - while March's season-opening Australian GP will mark the fourth anniversary of McLaren's last podium finish.
But for 2018 the team will be powered by Renault engines after three fruitless and frustrating seasons with Honda.
And the new McLaren is a successor to the MCL32 chassis which the team believed would have been a frontrunner in 2017 but for the crippling lack of power provided by its unreliable Honda units.
In 2018, McLaren's first yardstick will be their results relative to fellow Renault engine customers Red Bull as well as the Renault works outfit.
"We definitely view 2018 as the year when McLaren will move closer to the front, fighting teams and drivers as we improve our fortunes," said team boss Zak Brown.
And racing director Eric Boullier added: "I think the whole team feels proud of this car.
"The design, engineering and aerodynamic departments have done an incredible job delivering a new car with a new power unit in an extremely short timeframe. We never took the easy route or looked to shortcut a process or a solution, and the result is a car that is neat and well-resolved."
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