Luke James Colless, 32, pleaded guilty to five counts of rape and six of sexual assault over a 27-month period until July last year in the northeastern city of Brisbane.
The married father-of-four spotted women on the path on his way to work, then changed into running clothes and attacked them, the court heard.
Judge Marshall Irwin said Colless's victims felt "pure fear" and some believed they would not survive the ordeal.
"It appears as though your level of violence was escalating," Judge Irwin said. "You did not think you could stop until you were caught."
Irish tourist Kieran O'Neill, 33, may be in line for a 50,000 dollar (USD 42,000) reward after helping police snare Colless by following him and writing down his car number-plate.
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