Saudi's King Salman "ordered that Saudi investments in Egypt exceed 30 billion riyals ($8 billion)" and that the kingdom "contribute in providing Egypt with its needs for petrol," said a statement published by the Saudi Press Agency.
In addition, Saudi ships would "support" traffic in the Suez Canal, Saudi defence minister and Deputy Crown Prince Mohammed bin Salman announced on Tuesday during a visit to Egypt.
The pledges come despite a sharp fall in Saudi Arabia's income from oil, which makes up over 90 percent of public revenues, due to the global decline in crude prices since June last year.
OPEC kingpin Saudi Arabia has offered billions of dollars in aid to Egypt since the 2013 ouster of Islamist president Mohamed Morsi.
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In March, Saudi Arabia, Kuwait and the United Arab Emirates each offered $4 billion in investment and aid.
Egypt is taking part in a Saudi-led coalition that has been battling Iran-backed rebels in Yemen since March.
It is also participating in a 34-member alliance to fight "terrorism", which was announced on Tuesday by Prince Mohammed.
During his visit, Sunni Islam's leading seat of learning, Al-Azhar, urged all Muslim countries to join the new coalition.
Cairo is fighting a swelling insurgency led by the Islamic State group in the Sinai Peninsula.
But it has been criticised by rights group for carrying out a crackdown on Morsi's Muslim Brotherhood that left hundreds dead and tens of thousands imprisoned.