We introduce a new wildlife re-identification dataset WildlifeReID-10k with more than 214k images of 10k individual animals. It is a collection of 30 existing wildlife re-identification datasets with additional processing steps. WildlifeReID-10k contains animals as diverse as marine turtles, primates, birds, African herbivores, marine mammals and domestic animals. Due to the ubiquity of similar images in datasets, we argue that the standard (random) splits into training and testing sets are inadequate for wildlife re-identification and propose a new similarity-aware split based on the similarity of extracted features. To promote fair method comparison, we include similarity-aware splits both for closed-set and open-set settings, use MegaDescriptor - a foundational model for wildlife re-identification - for baseline performance and host a leaderboard with the best results. We publicly publish the dataset and the codes used to create it in the wildlife-datasets library, making WildlifeReID-10k both highly curated and easy to use.