Zhang Yiming, who helped found TikTok’s parent company, the Chinese internet conglomerate ByteDance, and turned it into a globe-straddling giant, will step down as chief executive at the end of the year to focus on long-term strategy, he wrote in a letter to employees dated Wednesday.

ByteDance’s co-founder and head of human resources, Liang Rubo, will take the reins as chief executive.

“After handing over my role as C.E.O., and removing myself from the responsibilities of daily management, I will have the space to explore long-term strategies, organizational culture and social responsibility, with a more objective perspective on the company,” Mr. Zhang wrote.

Mr. Zhang, 38, is also ByteDance’s chairman. The letter, which ByteDance posted on its website, did not address whether the leadership transition would affect his role in that position.

ByteDance, founded in 2012, is China’s first truly global internet company. With TikTok, it has achieved a level of commercial success and cultural influence that none of the country’s other tech powerhouses have managed outside China’s borders.