An engineer strode onstage at an event in Tehran, Iran, wearing tight pants and a stylish shirt, and clutching a microphone in one hand. Her long brown hair, tied in a ponytail, swung freely behind her, uncovered, in open defiance of Iran¡¯s strict hijab law.

¡°I am Zeinab Kazempour,¡± she told the convention of Iran¡¯s professional association of engineers. She condemned the group for supporting the hijab rules, and then she marched offstage, removing a scarf from around her neck and tossing it to the floor under a giant image of Iran¡¯s supreme leader, Ayatollah Ali Khamenei.

The packed auditorium erupted in cheers, claps and whistles. A video of Kazempour went viral on social media and local news sites, making her the latest champion for many Iranians in a growing, open challenge to the hijab law.