Julia Middendorf (born 31 January 2003) is a German tennis player.
Middendorf has a career-high WTA rankings singles ranking of 347, achieved in August 2023, and a best doubles ranking of No. 610, reached in November 2022.
She made her WTA Tour main-draw debut at the 2021 Stuttgart Open, after defeating Jana Fett and Tamara Korpatsch in the qualifying, but losing to Anett Kontaveit in the first round.
| W25 tournaments (0–2) |
| W15 tournaments (3–1) |
| Win | 1–0 | ITF Erwitte, Germany | W15 | Clay | Sofia Samavati | 3–6, 7–5, 6–2 | |
| Loss | 1–1 | ITF Monastir, Tunisia | W15 | Hard | Ma Yexin | 4–6, 2–6 | |
| Win | 2–1 | ITF Antalya, Turkey | W15 | Clay | Victoria Kan | 6–1, 4–1 ret. | |
| Win | 3–1 | ITF Erwitte, Germany | W15 | Clay | Martha Matoula | 3–6, 6–3, 6–4 | |
| Loss | 3–2 | ITF Stuttgart, Germany | W25 | Clay | Ella Seidel | 3–6, 1–6 | |
| Loss | 3–3 | ITF Braunschweig, Germany | W25 | Clay | Ella Seidel | 6–7(4), 3–6 |
| W15 tournaments (0–2) |
| Loss | 0–1 | ITF Monastir, Tunisia | W15 | Hard | Mariana Dražić | Yasmine Mansouri Elena Milovanović | 6–7(4), 0–6 | |
| Loss | 0–2 | ITF Gonesse, France | W15 | Clay (i) | Nicole Rivkin | Flavie Brugnone Tamara Čurović | 2–6, 3–6 |
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