Keeping Women and Girls Safe from the Start Act of 2021 This bill requires the Department of State to carry out activities under the Safe from the Start program to prevent, mitigate, and respond to gender-based violence in humanitarian emergencies around the world. (The Safe from the Start program addresses childhood exposure to violence.) These activities shall include (1) training and capacity building for humanitarian personnel; (2) deployment of, and support for, gender advisors and female humanitarian aid workers; (3) use of standards, guidelines, and best practices to address gender-based violence; (4) expanding and improving empowerment activities; and (5) establishing accountability mechanisms and monitoring and reporting tools to prevent and respond to incidents of sexual or other gender-based exploitation or abuse. The State Department must submit an annual report that includes an analysis of data and research regarding the key drivers of gender-based violence in humanitarian emergencies, as well as a detailed description of the programs, diplomatic efforts, and other activities taken to implement Safe from the Start.