SoftBank’s Masayoshi Son goes all in on AI, raises $11.1B in the largest junk bond sale ever

Masayoshi Son has never been one for half measures. The SoftBank founder and CEO, who famously turned a $20 million bet on Alibaba into one of the greatest venture capital wins in history, is now borrowing at near-double-digit interest rates to chase what he believes is the next transformative technology wave.

SoftBank raised $11.1 billion in high-yield bonds in late September, making it the largest junk bond sale in corporate history. The previous record holder was Numericable’s roughly $10 billion issuance back in 2014. Son’s message to the market was characteristically blunt: he’s “all in” on AI.

Inside the record-breaking deal

The bond offering was split across two currencies. The dollar-denominated portion totaled $10 billion in senior notes, carved into three tranches with escalating yields. The shortest tranche, $1 billion at 3.5 years, priced at 8.625%. The two larger tranches, $4.5 billion each at 5.5 and 7.5 years, priced at 9.25% and 9.75% respectively.

Then there was the euro component: two €500 million tranches yielding 7.125% over four years and 8% over six years, bringing the total euro portion to €1 billion.

Despite the steep pricing, investor appetite was strong. The deal was reportedly oversubscribed, meaning more money wanted in than SoftBank was willing to take.

The OpenAI connection

The proceeds from this bond sale aren’t going into some vague AI research fund. They’re being channeled primarily toward SoftBank’s massive commitment to OpenAI, the Sam Altman-led company behind ChatGPT that has become the centerpiece of the current AI boom.

SoftBank’s cumulative investment in OpenAI is expected to reach approximately $65 billion, which would give the company about 13% ownership when the deal is expected to close around early October 2026.

This bond issuance represents the third tranche of financing toward that commitment. Earlier in the year, SoftBank secured around $40 billion in bridge loans to get the AI investment engine running. The junk bonds effectively refinance portions of that bridge debt while providing additional liquidity for future moves, including potential mergers and acquisitions.

SoftBank has also been tapping Japanese retail investors through yen-denominated bond offerings throughout 2026, underscoring just how aggressively the company is leaning on debt markets to fund its strategy.

The bull case and the bear case

Son’s pitch is straightforward. He believes SoftBank can position itself as a leading platform provider in what he calls artificial superintelligence, the theoretical next stage beyond today’s generative AI.

There’s historical precedent for Son’s high-conviction bets paying off spectacularly. His early investment in Alibaba returned more than $100 billion.

The bear case is equally straightforward, though. SoftBank is piling on debt at yields approaching 10% during a period of elevated interest rates and broader economic uncertainty. The company’s leverage ratios are climbing, and the AI sector, while undeniably hot, has yet to prove that the current level of capital expenditure will translate into proportional returns.

There’s also the concentration risk. Putting $65 billion into a single company, even one as dominant as OpenAI, is the kind of bet that either looks visionary or catastrophic in hindsight.