The marriage took place at his Pali Hill residence in the western Mumbai suburb of Bandra, where a government registrar solemnised the ceremony that began around 7.15 p.m. and lasted about an hour.
Clad in a black suit, Khan sported a simple look. Rao was even simpler, wearing a white salwar-kameez and a green dupatta.
As with his films, Khan was choosy with his guests too. Those among the invitees included lyricist Javed Akhtar, brother-in-law and actor Raj Zutshi and Rani Mukherjee, who filled in as a bridesmaid.
Khan, 41, met Rao during the making of his 2001 hit film "Lagaan" (Tax), which was nominated for an Oscar in the foreign film category. Rao was one of the assistant directors of the film.
Though the ceremony was attended by only close family members, the three-day-long wedding reception to be held at the hill resort of Panchgani, 250 km south of here beginning Thursday, is expected to see a large number of guests.
They include Ashutosh Gowariker, Rani Mukherji, Bobby Bedi, Kunal Kapoor, Raj Zutshi, Ketan and Deepa Mehta, Rakeysh Omprakash Mehra and Baba and Tanvi Azmi. They were invited by SMS and will be ferried by limousines from here.
The Rao family will have another reception Jan 2 in Bangalore.
Incidentally, Panchgani is where Khan and Rao reportedly fell in love during the shoot of the film.
Seven luxury hotels have been booked completely for the Bollywood celebrities. Both of Khan's children from his first marriage with Reena Dutta - Junaid and Aaira - will attend the reception, the sources said.