Lightroom itself will not do this, but there are third party utilities that can perform this task. I don't remember their names, but if you search this forum, I'm sure you will find some suggestions.
Teekesselchen is a fast duplicate finder plug-in for Adobe Lightroom using EXIF meta-data. It is open source and free of charge. It requires Lightroom 3.x, 4.x, 5.x or CC 2015 and runs on Windows as well as on Mac OS X.
I have used this with Lr CC2015.10 with success.
Using Lightroom, it creates a Collection in the Collection Panel with thumbnails of any images it believes to be duplicates, then it is up to you to decide which ones to delete.
A hint: When viewing the 'duplicates' in the created Collection, use Ctrl+J to set the Expanded Cell Extras to show 1) Folder 2) cropped dimensions. This gives an immediate reference to each photos location and filesize. (eg. maybe the dupes are tiny exported jpgs )
Be aware: That if you use any software that works externally to Lightroom to delete photos, (such as PowerPhotos, AusLogics Duplicate Finder, etc), Photos that were in the Lr Catalog will now show as 'Missing' and you have more steps to tidy the catalog.