The meet began with Prime Minister Narendra Modi hoisting the Bharatiya Janata Party (BJP) flag at Jawaharlal Nehru stadium.
The day-long event will see Amit Shah's ratification as BJP's new national president.
A close aide of Modi, Shah took over as the president of the BJP July 9 after his predecessor Rajnath Singh was appointed the union home minister.
Registration for the meet began early in the day.
Satish Upadhyay, BJP head of the Delhi unit, will deliver the welcome address and will present a momento to Modi.
Home Minister Rajnath Singh, who is the outgoing party president, will address the gathering at around 11 a.m., which will be followed by a speech by Shah at around 11.30 a.m.
The event will be rounded up with a speech by Modi which is scheduled to begin at around 3.50 p.m.