As of February 9, Bezos' wealth stood at $112 billion, up from about $73 billion a year ago, according to Forbes. He also made the list's biggest annual gain, reporting $39 billion more than previous year.
Bill Gates has been the richest person in the world for 18 of the past 24 years.
Also, Acharya Balkrishna, the co-founder of FMCG company Patanjali Ayurved, was ranked 274th on the list with a net worth of $6.3 billion.
Mr O'Leary is one of the few Irish resident billionaires on the list and comes in with an estimated worth of $1.1 billion.
Their collective worth is $9.1 trillion, an 18 percent increase from a year ago.
The 10 richest Indians include Kumar Birla, ranked 127th overall with a fortune of $11.8 billion, Uday Kotak (143, $10.7 billion), Radhakishan Damani (151, $10 billion), Gautam Adani (154, $9.7 billion) and Cyrus Poonawalla (170, $9.1 billion).
The only child of Bettencourt, Francoise Bettencourt Meyers, is the runner up with a net worth of $42.2 billion.
The total combined net worth of this year's billionaires was US$9.1 trillion, up from US$7.7 trillion last year, with 1,490 members being self-made billionaires, up from 1,371 in 2017.
US President Trump, worth $3.1 billion, was ranked at 766 this year, falling from 544 in 2017.
The improvement in Mr Bezos' fortune is the biggest on record.
Eight Indian women have featured in Forbes list of the world's richest.
Others include Smita Crishna-Godrej and Leena Tewari, who chairs the privately held drugmaker USV India.