Phillip J. Gillespie was born in Frankston on 23 October 1975 and works as a police officer in the Victorian Police Force when not officiating cricket matches. He also supports the Richmond Tigers in the Australian Football League. Before moving into umpiring, he played for the Rowville Cricket Club in Melbourne, where he suffered injuries to his Achilles tendon, jaw and knee. Wanting to stay involved in the sport, he started umpiring in the Victorian Premier Cricket competition in 2009.
His officiating career progressed to domestic competitions when he made his List A debut during the England Lions tour of Victoria in February 2013. He went on to umpire eight matches in the Matador BBQs One-Day Cup, alongside two Women's National Cricket League matches including a 2015 semi-final between New South Wales and Victoria. He also stood in six matches during the 2015-16 Big Bash League season and four the following season, plus Women's Big Bash League fixtures like the 2016-17 semi-final at the Gabba. His first-class debut came on 15 February 2015 in a Sheffield Shield match between New South Wales and Victoria at Robertson Oval, where Doug Bollinger took a hat-trick from his end.
Gillespie joined the Australian National Umpire Panel after replacing Damien Mealey for the 2015-16 season, following his acceptance into the Australian Sports Commission National Officiating Scholarship program in 2015. On the international stage, his career includes standing in 1 test match, 15 One Day Internationals, 28 Twenty20 Internationals from 2022 to 2025, 1 Women's Test match in 2021, 15 Women's One Day Internationals from 2014 to 2025, and 10 Women's Twenty20 Internationals from 2014 to 2026. His international debut arrived during the West Indies women's tour of Australia in 2014, and he later stood in his first men's Twenty20 International between Australia and West Indies on 7 October 2022.