Donald Philip Tregonning OAM (26 November 1928 – 14 September 2022) was an Australian professional tennis player and coach.

Tregonning, a student of Melbourne coach Mick Sweetnam,[1] was a member of the international amateur and professional tennis communities, reaching the mixed doubles semi finals of the 1953 Australian Open,[2] playing twice in the quarter-finals of doubles competitions at the Australian Open (1949, 1953) and reaching the quarter-finals of the Wembley Professional Championships in 1953.

His clientele included Wimbledon finalist Kurt Nielsen, Wimbledon Ladies' Doubles Champion Angela Buxton, British Davis Cup player Bobby Wilson, Ashleigh Barty's coach Craig Tyzzer, Grand Slam competitor Elizabeth Peers-Little, Australian Open doubles finalist Cliff Letcher, Grand Slam competitor Greg Whitecross and "Australian Junior" finalists Bill Durham, Trevor Little, Sally Irvine.

Tregonning became a member at Grace Park Tennis Club and joined the Mick Sweetnam School of Coaching.

Sweetnam regarded Tregonning as more promising than his other student seven time Grand Slam champion Mervyn Rose.

[5] Tregonning married fellow Australian and nursing sister Claire Wendy Heskett[6] at the Church of Our Lady, London.

In 1949 Tregonning lost a Round 2 Australian Championships match against Bill Sidwell, but partnering Rose was able to secure a spot in the quarter-finals of the doubles competition.

[9] Tregonning received direct entry into the Men's Singles draw of the 1951 Wimbledon Championships but lost in the first round to Brazilian Armando Vieira.

During his 30 years coaching the Japan national team Tregonning coached Japanese Olympic quarter finalist Jun Kamiwazumi who would go on to play in the quarter-finals of the French Open mixed doubles competitions and Japanese player Toshiro Sakai who would go on to become a four time Asiad gold medalist and French Open doubles quarter finalist.