Workday shares popped more than 17% on a report that private equity firm Silver Lake is in talks to buy the human resources software maker.
Shares were halted multiple times in late afternoon trading and the company's market value last topped more than $50 billion following the report from Reuters.
The discussions have been ongoing in recent months, Reuters reported, citing sources familiar with the matter.
Workday and Silver Lake did not immediately respond to CNBC's request for comment.