On ESXi? Yes.
On a standalone, free-license ESXi device? No. You need vSphere Server (nee Virtual Center) to create templates.
On the free ESXi you can enable Tech Support Mode and then once that is enabled you can connect to the host via SSH and use:
vmkfstools -i source.vmdk dest.vmdk -d thin
Then you can create a new VM using the file just created as an “Existing Disk”.
It’s not as convenient as as a Template, but it’s better than nothing…