The jurors were told they could only reach that determination if they were sure of four “essential” matters concerning the deaths at the 1989 FA Cup semi-final.
They had to be convinced that overall match commander Chief Superintendent David Duckenfield owed a duty of care to those who died in the disaster, and that he was in breach of that duty of care.
Thirdly, they would need to be satisfied that his breach of duty caused the deaths and, fourthly, that it amounted to “gross negligence”.
They concluded it was unlawful killing by a 7-2 majority.
The conclusion was greeted with sobbing and cheers at the hearing in Warrington.
The jury also ruled that fan behaviour did not cause or contribute to the tragedy.
The Hillsborough disaster unfolded during Liverpool’s cup tie against Nottingham Forest on April 15 as thousands of fans were crushed at Sheffield Wednesday’s ground.
Mr Duckenfield gave the order at 2.52pm to open exit Gate C in Leppings Lane, allowing around 2,000 fans to flood into the already packed central pens behind the goal.
The jury also found that both the police and the ambulance service caused or contributed to the loss of lives in the disaster by an error or omission after the crush in the west terrace had begun to develop.
The jurors were given a round of applause as they left the courtroom.