| Ilse Koolhaas | |
| Nationality: | Dutch |
| Birth Date: | 11 June 1997 |
| Birth Place: | Ouderkerk aan de Amstel, Netherlands |
| Height: | 1.83 m |
| Weight: | 76 kg |
| Position: | Defender |
| L/R: | Right |
| Currentclub: | AS Orizzonte Catania |
| Clubs1: | OZ&PC de Snippen (-2007) HZC De Robben (2007–2011) ZVL Leiden (2011–2016) NC Vouliagmeni (2016–2018) AS Orizzonte Catania (2018–) |
| Nationalyears1: | |
| Nationalteam1: | Netherlands |
Ilse Koolhaas (born 11 June 1997) is a Dutch water polo player for AS Orizzonte Catania and the Dutch national team.[1]
She participated at the 2018 Women's European Water Polo Championship.[2]