The incredible sight dazzled those lucky enough to witness it just before midnight on Saturday (early Sunday AEST).
Many videos shared on social media captured a bright flash of light almost turning day to night as the projectile streaked through the atmosphere with either a greenish or bluish hue.
The footage was captured in Porto and other parts of the country by security cameras, dash cams and even people partying or watching concerts.
Spanish astronomers who followed the meteor's path, said it entered the atmosphere at 161,000km/h but stopped being visible 54 kilometres above the ground.
It's unclear whether the meteor hit the Earth's surface. The Portuguese Civil Protection agency received reports of a meteorite landing in the municipality of Castro Daire, about 65 kilometres south-east of Porto but crews sent to investigate found no sign of it.
But a Portuguese astrophysicist said the meteor may not have landed at all.
Nuno Peixinho from Coimbra University's Institute of Astrophysics and Space Sciences said images captured by a Spanish meteor observation network appeared to show the meteor vaporising while still more than 50 kilometres above the earth's surface.
"The burst of light we saw is precisely the object vapourising itself," he told CNN Portugal. "An object like this enters the atmosphere at a velocity between 10 and 70 kilometres per second.
"This one entered at 45. It was already pretty big and fast."
Peixinho said meteors were common but "fireballs" such as this one were rarer, particularly in a small country such as Portugal.
He said the noise heard by many witnesses only meant that the meteor was large, not that it hit the earth to become a meteorite.
