The 68-year-old movie mogul has been dating the 43-year-old businesswoman, who is the president of Ariel Investments, since 2006.
Hobson has never been married before, while Lucas was married to Marcia Lucas from 1969 to 1983, reported Aceshowbiz.
The director-producer has had an eventful past few months - he sold his production company LucasFilm to Disney for a whopping USD 4.05 billion, then donated the bulk of the money to an education fund.
The mogul and his fiancee rang in 2013 at Russian billionaire Roman Abramovich's star-studded party on a super yacht in St Barts.