The 37-year-old, seeded third, is bidding to extend his all-time leading men's Grand Slam record to 21 title and would capture a 100th ATP tournament win in the process.
The pair have met four times in Australian Open finals, with the Serb winning them all.
The draw for the first Grand Slam of the season was made on Thursday and the top seeds could face some early tests of their title credentials when play gets underway on Monday.
Should Djokovic, a six-time victor at Melbourne Park, beat an as-yet-unknown qualifier, he could face wildcard Jo-Wilfried Tsonga in the next match, with Denis Shapovalov a possible third-round opponent and Kei Nishikori potentially awaiting in the last eight.
British number one Kyle Edmund, who reached the semi-finals a year ago, has a hard draw against Tomas Berdych.
"I always enjoy my matches against him", 20-time grand slam victor Federer said at the draw.More news: Meghan Markle and Prince Harry's $4.5m temporary farm home
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Six-time Melbourne Park champion Federer, seeded No.3 for his quest for a hat-trick of Australian Open crowns and a record seventh AO titles in all, opens his 2019 campaign against world No. 99 Denis Istomin, while fellow six-time Melbourne victor and men's top seed Novak Djokovic plays a qualifier in the first round.
Second seeded Nadal begins against Australian James Duckworth, fourth seed Alexander Zverev faces Slovenian Aljaz Bedene while last year's runner-up Marin Cilic has a tricky encounter with Australian Bernard Tomic.
Romanian Halep was named the top seed in women's singles, followed by Angelique Kerber of Germany and Denmark's Caroline Wozniacki. He defeated Tsonga in the 2008 Australian final.
"I'm so close, I'll give it a go", Federer said.
In an interview to The Times of India, the three-time Grand Slam victor Stan Wawrinka commented on the Big Three's dominance.