Short for “Modified National Institute of Standards and Technology," MNIST is the canonical database of labeled images of handwritten digits from 0 through 9. MNIST is often used in sample projects as a sort of "hello world" for machine learning. It is also used frequently as a performance benchmark.
The dataset has a training set of 60,000 examples, and a test set of 10,000 examples which are available from this page.
MNIST is available in the Public Datasets Repository which is provided for free in Gradient. These datasets are automatically mounted to every Notebook and Experiment.