SoftBank Group said it led a $1 billion investment in US financial technology start-up 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 SA 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 US", SoFi CEO and co-founder Mike Cagney said in the statement.
SoftBank is a long time investor in tech start-ups, with Alibaba Group and Yahoo Japan among those 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 US mobile phone carrier Sprint to 83.19% from 81.99%, less than two months after its last incremental purchase.
The purchases are being closely watched by investors as a holding of 85% could see Sprint delisted under New York Stock Exchange rules. SoftBank has said it doesn't expect to reach 85%.