Bertrand Yansouni, a veteran sales executive who joined Google Cloud last November to help manage relationships with business partners, is leaving the company, according to three people familiar with the matter. His departure comes at a crucial time for Google Cloud as it seeks to get customers and make headway against rivals Amazon Web Services and Microsoft Azure.

Mr. Yansouni has been leading Google Cloud’s relationships with resellers, professional services firms, telecom carriers and other business partners who help promote the company’s cloud services. His role was critical to efforts by Diane Greene, who runs the business unit, to grow Google Cloud’s market share.