Early life and education
Patrick Anthony Keane was born to Patrick and Margaret Keane in a family of Irish descent  and raised in Wilston, a middle-class, inner-city suburb in northern Brisbane, Queensland. Patrick Keane senior was an RAAF aviator who died from a heart attack when the younger Patrick was seven.
Keane was educated at Catholic schools: St. Columba's Convent School and St. Joseph's College, Gregory Terrace in Brisbane,  where he was the school captain and dux of 1969, winning an Open Scholarship in the Queensland Senior Public Examinations.  After eliminating other vocations, he graduated from the University of Queensland with a Bachelor of Arts in 1973, and a Bachelor of Laws with first-class honours and a University Medal in 1976. 
Keane read for a Bachelor of Civil Law at Magdalen College of the University of Oxford and was awarded the Vinerian Scholarship, a scholarship given to the student that "gives the best performance in the examination for the Degree of Bachelor of Civil Law".  Having earned a B.C.L. with First-Class Honours in 1977, he then returned to Australia.
Keane was admitted as a Solicitor and Barrister of the Supreme Court of Queensland in 1976 and went to the bar, as a Barrister of the Supreme Court of Queensland, in 1977.  During 1978–1979, he was a part-time lecturer at the University of Queensland. 
In 1992, Keane was appointed Solicitor-General for the State of Queensland, a position he held under Labor and Coalition state governments until his appointment to the Court of Appeal of the Supreme Court of Queensland.  
Keane published a number of articles and has been outspoken on the quality of legislative drafting. During 1990–1992, he was the Deputy Chairman of the Queensland Law Reform Commission.  In 2011, he condemned the "volume and complexity of federal laws", telling the Australian Financial Review that "opening the tax act is like entering the door to a parallel universe". 
In 2005, Keane was appointed a Judge of Appeal of the Court of Appeal of the Supreme Court of Queensland, the highest court in that state. 
On 10 February 2010, Commonwealth Attorney-General Robert McClelland announced that Keane would be appointed as the next Chief Justice of the Federal Court of Australia.  Keane took up that role on 22 March 2010. 
On 8 June 2015, he was named a Companion of the Order of Australia for eminent service to the law and to the judiciary, through contributions to improved legal and public administration, as an advocate for increased access to justice, to ethical standards, and to a range of professional organisations. 
High Court career
On 20 November 2012, Attorney-General Nicola Roxon announced that Keane had been appointed a Justice of the High Court of Australia effective on the retirement of Dyson Heydon on 1 March 2013.  Keane became the 50th Justice appointed to the High Court.  Keane's position as Chief Justice on the Federal Court bench was filled by James Allsop, the president of the NSW Court of Appeal. 
In 1974, aged 22, Keane married Shelley, with whom he has three sons and five grandchildren. His wife, Dr. Shelley Keane, is a psychologist. His son Patrick was born in Oxford in December 1976. His son David is a barrister.
The Australian reported that Keane is said to have been close to former Prime Minister and fellow Queenslander Kevin Rudd and that Keane has been described by one unnamed Brisbane barrister as a "Labor man".  Keane's appointment met with bipartisan approval: the Liberal Party's justice spokesperson, Senator George Brandis, described Keane's appointment as "the right decision" and Keane himself as a "very, very distinguished lawyer, both academically and professionally" with "a very illustrious reputation".