TOKYO, Japan — SoftBank Group Corp.'s Vision Fund will invest $2 billion in South Korea's Coupang, giving the e-commerce giant funds to accelerate development of new shopping and delivery services.

Coupang, founded in 2010, is Korea’s largest online retailer, selling more than 120 million items from consumer electronics to food. The Seoul-based company says that half of Korea’s population has downloaded its mobile app.

The deal marks another enormous bet on e-commerce for SoftBank founder Masayoshi Son, who made a fortune backing Alibaba Group Holding before it turned into China’s dominant provider. SoftBank put an initial $1 billion investment into Coupang in 2015, valuing it at $5 billion, according to people familiar with the matter. The valuation in the current deal is $9 billion post-money, or after the additional capital is included, the people said.

"Masa is a visionary leader. He’s always challenged us to think big," said Bom Kim, founder and chief executive. "This round came from understanding that what we’ve built is now the foundation for immense impact on customers."

The investment is one of SoftBank’s biggest since the suspected assassination of a journalist by Saudi Arabian agents that sparked a global outcry. The brutal murder escalated scrutiny of SoftBank’s ties to Saudi Arabia, which contributed $45 billion to the nearly $100 billion Vision Fund. Son had been planning to raise the same amount every two to three years, but it’s unclear if he can achieve that goal without more money from Saudi Arabia.

With the previous $1 billion investment from SoftBank, Coupang built its own fulfilment and last-mile delivery infrastructure, according to Lydia Jett, an investor at Vision Fund focused on consumer internet and e-commerce. Earlier this year SoftBank had been in discussions with the company about raising a smaller slice of money ahead of a potential public offering in 2019. Yet as SoftBank observed Coupang’s accelerating growth, the firm decided that it would be best to give Coupang a larger cash infusion so it can grow its business before subjecting it to the public markets.

"It will be a public company in the not too distant future, but just not 2019,” said Jett, who sits on Coupang’s board. “It’s going to give them runway to make investments in new categories.”

The startup is a rare success story in country where 10 family-run conglomerates control more than a quarter of all business assets. Its early push into e-commerce and fast delivery helped maintain its lead. Rocket Delivery service promises to get goods to customers within 24 hours, while Coupang Fresh delivers produce to customers within hours of ordering. Firms that have invested in the company include BlackRock, Sequoia Capital and Wellington.

Revenue has more than doubled in the last two years and is forecast to reach nearly $5 billion by year-end, according to the company. Though the company is focused on reaching Korean consumers, it has offices in Beijing, Los Angeles, Seattle, Seoul, Shanghai and Silicon Valley.

By Selina Wang; editors: Robert Fenner, Peter Elstrom and Reed Stevenson