Jack Liangjie Xu (simplified Chinese: 许良杰; traditional Chinese: 許良傑), more commonly known as Jack Xu in English, is a Chinese software engineer, technology executive, and venture capitalist. He is the former Co-President and Chief Technology Officer (CTO) of SINA Corporation, the operator of Sina Weibo, the most influential social network in China.He formerly worked as the Corporate Vice President for Cisco's Unified Communications business unit, Vice President of Engineering & Research at eBay, and CTO at NetEase.