The former army general, who was first elected in 2014, made the announcement in a televised address.
“As I have in the past answered the call of Egyptians, here I am today answering their call once again,” said Mr El Sisi, 68.
“I have decided to nominate myself for you so we can continue the dream in a new presidential term that I promise will be a continuation of our joint endeavour for the sake of Egypt and its people.”
His win is widely considered to be virtually guaranteed given his access as the incumbent to the state's vast resources, including the media and government institutions.
Many Egyptians also feel an aversion towards change after the years of turmoil that followed a 2011 uprising, which forced long-serving autocratic leader Hosni Mubarak to step down.
Egyptians have also grown accustomed to leaders hailing from the military, with many believing they provide a safe pair of hands in a region often in turmoil.
Should he win the election, Mr El Sisi will have served 16 years in office when his third term ends in 2030.
“I sincerely call on Egyptians to make this election the new beginning of an energetic political life that boasts diversity,” he said in his address.
Thousands of his supporters were gathered on major squares in cities across the country ahead of the announcement, where they waved flags as giant screens showed the president's address to the nation.
The December elections will be held as the country of 105 million people is suffering an economic crisis during which the Egyptian pound lost half its value since March 2022 and inflation hit record highs.
A persistent foreign currency crunch has suppressed imports and badly hurt industries dependent on foreign materials.
Mr El Sisi has blamed the crisis entirely on the coronavirus pandemic and the Russia-Ukraine war, but critics maintain that overspending and excessive borrowing – the foreign debt stands at more than $160 billion – were major contributing factors.
His announcement on Monday night came at the end of a three-day forum in which he listened to his Prime Minister and Cabinet members speak at length about the achievements of the government in the nine years since Mr El Sisi took office.
On Saturday, he urged Egyptians to make do with less, saying it was better if they went hungry and thirsty if that meant building the nation and achieving prosperity.
Mr El Sisi will be challenged in the December vote by Ahmed Tantawy, an outspoken former member of parliament and a critic of the Egyptian leader.
Mr Tantawy has been gaining popularity since he declared his intention to run earlier this year.
The other challengers are lesser known politicians, with limited popular appeal.
“As an Egyptian citizen before being President, I am very happy to see this multitude of candidates who are taking the initiative to take responsibility," Mr El Sisi said.
"They have my respect and appreciation.”