SoftBank said it had led a $1 billion investment in U.S. financial technology startup SoFi, calling it the largest single financing round in the fintech space to date.
The deal is the latest in the sector, where relatively young companies offer financial services through software. In July, Spain's Banco Santander agreed to provide up to around $16 million for any opportunities it identifies with British mobile banking software partner Monitise.
Other investors in SoFi, which refinances student loans and mortgages, included private equity firm Third Point.
SoftBank and SoFi said a joint statement that the Series E funding round will accelerate SoFi's growth as a financial services partner for consumers disenchanted with traditional banking.
SoFi aspires to be "the most trusted financial services partner in the U.S.," SoFi CEO and co-founder Mike Cagney said in the statement.
SoftBank is a longtime investor in tech startups, with Alibaba and Yahoo Japan among in its portfolio. More recently, it led a $500 million investment in Indian online marketplace Snapdeal in August, and put $250 million into Singapore-based ride hailing app GrabTaxi at the tail end of last year.
Separately, SoftBank said it had raised its stake in U.S. mobile phone carrier Sprint Corp to 83.19 percent from 81.99 percent, less than two months after its last incremental purchase.
The purchases are being closely watched by investors as a holding of 85 percent could see Sprint delisted under New York Stock Exchange rules. SoftBank has said it doesn't expect to reach 85 percent.
Shares of SoftBank ended morning trade up 2.7 percent, compared with a 1.7 percent rise in the benchmark index.