Alwaleed already owns a seven per cent stake in News Corp and plans to start a cable news channel.
The Twitter stake, bought jointly by Alwaleed and his Kingdom Holding Company investment firm, resulted from “months of negotiations”, Kingdom said.
Twitter chief executive Dick Costolo valued the company at $8bn in October, according to media reports, which would peg the size of Alwaleed’s investment at just under 4pc.
Bernhard Warner, co-founder of analysis and advisory firm Social Media Influence, said: “The Arab world, of course, knows full well the value of Twitter.
“(Alwaleed) must see Twitter as something that is going to be a really powerful broadcast channel,” he said, adding the Saudi had got into the Internet boom belatedly, with mixed results, and appeared to be “kind of late” to the game again.
Investors in Saudi Arabia were more bullish, sending shares in Kingdom up 5.7pc to 8.30 riyals at the close.
“One of the few sectors to record significant revenue gains in the last three years has been technology, which is why Kingdom would see Twitter as a good addition to its diversified portfolio,” said Hesham Tuffaha, head of asset management at Bakheet Investment Group in Riyadh.