David Marcus, the executive leading Facebook Inc.’s blockchain efforts and new Libra cryptocurrency, will testify before Congress to answer questions about the initiative.

Marcus said in a blog post July 3 that he will represent Facebook on July 16 and July 17 in front of U.S. Senate and House committees looking into the company’s plans for the cryptocurrency, which was announced last month. “We are looking forward to continuing to engage with the various communities and stakeholders,” he wrote.

Marcus, in the blog, said he wanted to clear up “misunderstandings” he has heard about Libra over the past two weeks....