Clemens Trimmel (born 8 June 1978) is a former professional tennis player from Austria.
His only Challenger title came in 2000 at the Oberstaufen Cup, where he defeated Radomír Vašek in the final. He was unable to defend his title in 2001 but did have a win over David Ferrer.
At the 2001 French Open he made it to the final round of qualifying, beating James Blake en route.
In 2012 he was appointed Austria's Davis Cup captain and in his first year took the team to the World Group quarter-finals, for the first time since 1995. The Austrians were relegated in 2013 and after their 2014 campaign, in which they were unable to return to the World Group, Trimmel was replaced by Stefan Koubek. He also captained the Austria Fed Cup team in the 2014 season.
| {class=wikitable style=font-size:97% !Legend |
| ATP Challenger (1–4) |
| ITF Futures (5–1) |
| Hard (0–1) |
| Clay (6–3) |
| Grass (0–0) |
| Carpet (0–1) |
| Loss | 0–1 | Skopje, Macedonia | Challenger | Clay | Dušan Vemić | 3–6, 7–6, 3–6 | |
| Loss | 0–2 | Ansfelden, Austria | Challenger | Clay | Markus Hipfl | 2–6, 0–6 | |
| Loss | 0–3 | Morocco F2, Casablanca | Futures | Clay | Pedro Rico Garcia | 4–6, 6–4, 6–7 | |
| Win | 1–3 | Cyprus F1, Nicosia | Futures | Clay | Óscar Burrieza López | 6–3, 6–4 | |
| Win | 2–3 | Austria F1, Salzburg | Futures | Clay | Charles-Edouard Maria | 6–2, 6–4 | |
| Win | 3–3 | Austria F2, Telfs | Futures | Clay | Thomas Schiessling | 6–4, 6–4 | |
| Win | 4–3 | Germany F4, Mannheim | Futures | Clay | Nikolay Davydenko | 2–6, 6–1, 6–4 | |
| Win | 5–3 | France F11, Noisy-le-Grand | Futures | Clay | Albert Montañés | 6–1, 7–6(7–5) | |
| Win | 6–3 | Oberstaufen Cup, Germany | Challenger | Clay | Radomír Vašek | 6–4, 6–1 | |
| Loss | 6–4 | Cherbourg, France | Challenger | Hard | Orlin Stanoytchev | 4–6, 6–3, 5–7 | |
| Loss | 6–5 | Magdeburg, Germany | Challenger | Carpet | Axel Pretzsch | 4–6, 4–6 |
| {class=wikitable style=font-size:97% !Legend |
| ATP Challenger (0–1) |
| ITF Futures (1–1) |
| Hard (1–0) |
| Clay (0–2) |
| Grass (0–0) |
| Carpet (0–0) |
| Loss | 0–1 | France F4, Deauville | Futures | Clay | Jérôme Haehnel | Juan Gisbert-Schultze Marcos Roy-Girardi | 6–4, 4–6, 4–6 | |
| Win | 1–1 | Croatia F2, Zagreb | Futures | Hard | Ivo Karlović | Tapio Nurminen Janne Ojala | 6–4, 6–4 | |
| Loss | 1–2 | Oberstaufen Cup, Germany | Challenger | Clay | Thomas Strengberger | Karol Beck Branislav Sekáč | 6–2, 1–6, 0–6 |
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