There are two MKV players named VLC Media Player and MPlayer OS X. These excellent and free multimedia players can tackle many of the video formats unknown to QuickTime. They contain a decoder to decode the .mkv files. They will also play many of the formats you will find inside the .mkv file.
Mac MKV Player Freeware - Using VideoLAN VLC Media Player - VLC player supports all the video and audio streams you will find in an MKV file. You need not to install any codecs or filters to play .mkv files.
Media Player Classic has a built in DVD player with real-time zoom, support for AVI subtitles(learn how to convert MKV to AVI), QuickTime and RealVideo support (requires QuickTime and/or Real Player), built-in MPEG2/SVCD/DVD codec. To play mkv file you need to install updated Matroska Pack.
At times you need a Mac MKV[1] Converter Software
WinX HD Video Converter for Mac is most popular Mac MKV Converter software. It fully supports Multi-core CPU (i3, i5, i7), and armed with Hyper Threading Technology (Converting MKV by multi threads at the same time, speed up the conversion timely). That is why WinX MKV converter program can be the fastest solution in the current market. Free Download to Experience>>
Other Tips about MKV file
1. Convert M2TS to MKV: allows you make HD video source from internet to digital content that playable upon your Blu-ray player and PS3 Xbox.
2. Rip DVD to MKV for digital backup DVD content and watch MKV on PS3 Xbox and Blu-ray player.
3. Convert MKV to AVI, then you can get PC friendly video file to playback on computer smoothly.
4. Convert MKV to MP4, make your MKV video commonly used format on Mac OS X, iPhone, iPad.
Related External Source
[1]: Matroska MKV Video Knowledge from MKV Official Site