The project is expected to build out all 200 gigawatts of the project by 2030, Masayoshi Sons said.
The crown prince is pursuing structural reforms in Saudi Arabia to reduce the reliance of the country's economy on oil.
Softbank Group Chairman and CEO Masayoshi Son and Saudi Arabia's Crown Prince Mohammed bin Salman reached the agreement in NY on Tuesday. Mohammed is now touring the United States in an effort to woo foreign investment in the kingdom as part of his effort to transform and diversify the economy there.
"You have never seen something of this scale", he is reported as saying.
The deal was signed in presence of Saudi Crown Prince Mohammed bin Salman who is on a USA visit.More news: Mexico official: Iowa family died from water heater gas leak
Vision Fund also plans investing 10 billion Dollars in state-controlled Saudi Electricity as part of efforts to diversify electricity production with renewable energy and solar power.
"The kingdom has great sunshine, great size of available land, great engineers, great laborers", he said. The development will reach its maximum capacity by 2030 and may cost close to US$1 billion a gigawatt, he said.
Masayoshi Son said the project would create 100,000 jobs and reduce the cost of producing by 40 billion Dollars. About two-thirds of this energy was generated by natural gas and the rest by oil.
SoftBank plans to invest 25 billion United States dollars in Saudi Arabia in the next three or four years.
SoftBank's Son added that the electricity produced in the first phase will be sold and that would help financers to earn money for the forthcoming stages. At $93 billion it's not large enough to pay for the mammoth solar project, but it's thought the fund will contribute to some of its costs. SoftBank is said to have aimed to deploy as much as US$15 billion in a new city called Neom, which the crown prince plans to build on the Red Sea coast.
The deal is the first major investment by the fund in Saudi Arabia. The kingdom's sovereign wealth fund has reportedly committed $45 billion to the massive technology investment vehicle, which counts Uber, Nvidia and WeWork among its largest investments. The electricity demand in the country has grown by 9% a year since 2000.