SoftBank’s record $11.1 billion junk bond sale raises the stakes on Son’s AI bets

SoftBank Group just borrowed more money in the junk bond market than any company ever has. The Japanese conglomerate raised $11.1 billion on September 24, 2026, in the largest high-yield corporate bond issuance on record.

Where is most of that cash going? Straight into OpenAI. That makes CEO Masayoshi Son’s already concentrated wager on artificial intelligence even more concentrated, and noticeably more expensive to carry.

The deal by the numbers

The sale knocked Numericable out of the record books. The French telecom group had held the title for the biggest junk-bond deal since 2014.

Proceeds primarily covered the final $10 billion tranche of SoftBank’s $30 billion follow-on investment in OpenAI. With that payment, SoftBank’s total investment in the ChatGPT maker reaches $64.6 billion. The money buys it an approximate 13% stake.

The pricing tells its own story. SoftBank sold dollar notes in three maturities, and each one came with a hefty coupon:

• 3.5-year notes: 8.625%
• 5.5-year notes: 9.25%
• 7.5-year notes: 9.75%

Those are the highest rates SoftBank has paid in its history. All three tranches carry a BB+ rating, which sits one notch below investment grade.

The package also included €1 billion in euro-denominated notes. The deal settled around September 29.

Demand reportedly exceeded four times the amount on offer in some tranches.

Why borrow instead of sell

SoftBank could, in theory, fund OpenAI by selling some of its holdings that have gained value. It chose debt instead. The move reflects a strategy of managing its existing obligations without dumping appreciated assets during a volatile market.

SoftBank’s shares have fallen 38% since their June 2026 peak.

SoftBank’s credit default swap spreads widened by 24% between June and October 2026.

Meanwhile, the OpenAI checks are not SoftBank’s only big outlays. The company has completed a deal for ABB’s robotics business at $5.4 billion and another for DigitalBridge at $3.1 billion.

What this means for SoftBank and AI investors

The most immediate implication is pressure on Son. He has now financed a large slice of his OpenAI position with debt that costs as much as 9.75% a year. That interest bill arrives on schedule regardless of how AI sentiment trades in any given quarter.

The deal also sends a mixed signal about how markets view AI. Oversubscription of four times in some tranches shows real appetite for exposure to the sector, even through a high-yield wrapper. The record coupons, though, show lenders want to be well compensated for the concentration risk.

Competitively, the $64.6 billion commitment cements SoftBank’s place among the heavyweight backers of AI, alongside players like Amazon and Nvidia.