Guillaume Couillard (tennis player)

Guillaume Couillard (born 10 December 1975) is a professional Monegasque former tennis player and a coach. Couillard reached his career-high ATP Tour singles ranking of World No. 569 in October 2002. He primarily played on the Futures circuit and the Challenger circuit.

Coaching career
He is currently coaching Monegasque players Hugo Nys, Romain Arneodo and Lucas Catarina.

Tennis career
Couillard was a member of the Monegasque Davis Cup team since 2002, having posted a 14–10 record in singles and a 13–10 record in doubles in thirty-five ties played.

In 2013, Couillard and Benjamin Balleret played the longest known tiebreak in professional tennis history, lasting 70 points (34–36). Couillard lost the match 6–7(34), 1–6 in the third qualifying round for the USA F1 Futures in Plantation, Florida.