Father's Day is a celebration honoring fathers and celebrating fatherhood, paternal bonds, and the influence of fathers in society. Many countries celebrate it on the third Sunday of June but it is also celebrated widely on other days. Father's Day complements Mother's Day, a celebration honoring mothers.

Father's Day is a celebration of fathers inaugurated in the early twentieth century to complement Mother's Day in celebrating fatherhood and male parenting.

Credit for what we now recognize as the official Father's Day goes to Sonora Smart Dodd, born in Arkansas from Spokane, who invented her own celebration of Father's Day in 1910. Its first celebration was in Spokane, Washington on June 19, 1910. Her father, the Civil War veteran William Jackson Smart, was a single parent who reared his six children in Spokane, Washington. Although she initially suggested June 5, her father's birthday, she did not provide the organizers with enough time to make arrangements, and the celebration was deferred to the third Sunday of June.

The Milperra Massacre was a firearm battle between rival motorcycle gang members on September 2 (Father's Day) 1984, in Milperra, a south-western suburb of Sydney. The massacre had its beginnings after a group of Comancheros broke away and formed the first Bandidos Motorcycle Club chapter in Australia resulting in intense rivalry between the two chapters. Seven people were killed: six motorcycle gang members and a fourteen year old female bystander.

Police believe that the war began over turf or drugs, however, the clubs at that time had a strong no drugs policy and Colin Ceasar Campbell, former Sergeant-at-Arms of the Harris Park based Comancheros and then President of the Birchgrove chapter until they were "patched" as Bandidos, points to the acrimony of the split as the sole reason. According to Campbell, in late 1983, one of his brothers and another Comanchero had called on another member and caught Comanchero president Jock Ross in a compromising position with the members wife. As Sergeant-at-Arms, he ordered Ross to face charges of breaking one of the 10 firm rules the club observed. If found guilty, Ross would have been expelled from the club. Ross failed to appear at the first two scheduled meetings and after arriving at the third, simply announced that the club would be split into two chapters and walked out. Campbell, his four brothers, the three McElwaine brothers, Anthony Snodgrass Spencer (Snoddy), Charles Charlie Sciberras and several others who supported bringing charges against Ross set up a new Comanchero chapter in Birchgrove.