[closedcontour]

If you're looking for something worldwide, your best starting point is likely SRTM[1].

If you get into more specific areas you can generally find higher resolution data.

Good luck.

[1] - https://www2.jpl.nasa.gov/srtm/

[ge96]

Thanks for the rec

[ryandrake]

Also consider ETOPO1 [1]. SRTM is kind of old and is treetop instead of groundlevel which may matter for your application.

1: https://www.ngdc.noaa.gov/mgg/global/