The three, who all denied the charge of working with the now banned Muslim Brotherhood, included Australian Peter Greste and Canadian-Egyptian national Mohamed Fahmy, Cairo bureau chief of Al Jazeera English.
The third defendant, Egyptian producer Baher Mohamed, was given an extra three years for possessing a single bullet at the hearing attended by Western diplomats, some of whose governments summoned Egypt's ambassadors over the case.
The men have been held at Egypt's notorious Tora Prison for six months, with the case becoming a rallying point for rights groups and news organsiations around the world.
They were detained in late December and charged with helping "a terrorist group" - a reference to the Muslim brotherhood - by broadcasting lies that harmed national security and supplying money, equipment and information to a group of Egyptians.
The Brotherhood was banned and declared a terrorist group after the army deposed elected Islamist president Mohamed Mursi in July following mass protests against his rule. The Brotherhood says it is a peaceful organisation.
Al Jazeera, whose Qatari owners back the Brotherhood and have been at odds with Egypt's leadership since he was ousted, said the ruling defied "logic, sense and any semblance of justice".
"There is only one sensible outcome now. For the verdict to be overturned, and justice to be recognised by Egypt," Al Jazeera English managing director Al Anstey said in a statement.
The ruling came a day after U.S. Secretary of State John Kerry met newly elected Egyptian President Abdel Fattah al-Sisi in Cairo and raised the issue of the journalists.
On Monday, Kerry said he called Egypt's foreign minister to register his "serious displeasure" over the "chilling and draconian verdict".
The courtroom quickly descended into chaos as the verdict was read out. Shaken and near tears, Greste's brother Michael said: "This is terribly devastating. I am stunned, dumbstruck. I've no other words."
The three men had looked upbeat as they entered the courtroom in handcuffs, waving at relatives who had earlier told journalists they expected them to be freed for lack of evidence.
One Dutch woman and two Britons were sentenced to 10 years in absentia on the same charges of aiding a "terrorist group".
Judicial sources told Reuters the verdicts could be appealed before a higher court and a pardon was still possible.
Egypt's public prosecutor last week ordered the release of another Al Jazeera journalist, Abdullah al-Shamy, on health grounds after he spent more than 130 days on hunger strike.
WESTERN CONDEMNATION
Western governments and rights groups have voiced concern over freedom of expression in Egypt since Mursi was ousted. The crackdown has reinforced doubts about Egypt's democratic credentials three years after an uprising toppled Hosni Mubarak and raised hopes of greater freedoms.
The case comes after a similar outcry over mass death sentences being handed down to Brotherhood supporters.
"Egypt's reputation, and especially the reputation of its judiciary as an independent institution, are at stake," U.N. human rights chief Navi Pillay said. "There is a risk that miscarriage of justice is becoming the norm in Egypt."
Britain, whose ambassador was one of several Western diplomats to attend the hearing, said it was summoning the Egyptian ambassador to protest about Monday's ruling.
"Freedom of the press is a cornerstone of a stable and prosperous society," Foreign Secretary William Hague said.
The Dutch foreign minister also summoned Egypt's ambassador. Australian Foreign Minister Julie Bishop said her government was "deeply dismayed that any sentence was imposed" and was "appalled by the severity of it".
Despite Kerry's condemnation on Monday, U.S. concerns have been balanced by an acknowledgement of the importance of Egypt as a longstanding strategic partner in the Middle East.
As well as discussing the transition to democracy, Kerry said on Sunday Egypt would be given aid in the form of Apache helicopters to use against militants in the Sinai peninsula that borders Israel, highlighting the multiple interests Washington is juggling.
Amnesty International called it a "dark day for media freedom" and other rights groups also condemned the verdicts.
"These... verdicts are a stark admission that in today's Egypt, simply practicing professional journalism is a crime and that the new constitution's guarantees of free expression are not worth the paper they are written on," said Sarah Leah Whitson from Human Rights Watch.
Egyptian officials have said the case is not linked to freedom of expression and that the journalists raised suspicions by operating without proper accreditation.
Many Egyptians see Al Jazeera as a force determined to destabilise the country, a view that has been encouraged in the local media, which has labelled the journalists "The Marriott Cell" because they worked from a hotel of the U.S.-based chain.
A video that appeared on a pro-government channel and spread online, reinforced the view that the journalists had sinister intents, showing their arrest in their hotel room, with close-ups of their computers, cameras and communications equipment allegedly used to broadcast lies aimed at undermining security.
Al Jazeera's Cairo offices have been closed since July 3 when security forces raided them hours after Mursi was ousted and criticism of the government and army has virtually vanished from the gamut of Egyptian media since then.
In total, 20 people were sentenced on Monday. They included at least 14 Egyptian defendants who faced charges of belonging to the Muslim Brotherhood.
Of those, two were acquitted including Anas al-Beltagi, the son of a senior Brotherhood official who is in jail. Four recieved seven-year sentences and the rest 10 years in absentia.
