Colloquy is an advanced IRC & SILC client which aims to adhere to Mac OS X interface conventions.

Features:

• AppleScript: A powerful dictionary for easy scripting.
• Solid IRC & SILC Cores: Powered by Irssi & the SILC Toolkit.
• Plug-In Love: Unlimited extensability through Plug-Ins.
• Styled For You: Pick the look for your conversations.
• Colors of the World: Fully compatible with mIRC colors.
• Open Minded: Open source, like it should be.
• Unintrusive Interface: Sleek multi- or single-window modes.
• File Transfer Medly: Full DCC transfer support with resume.
• They're Your Buddies: A buddy list for your IRC friends.
• Express Yourself: Use the emotions that speak for you.
• Multiplicity: The freedom to chat on multiple servers.

Colloquy is freeware. However, if you enjoy using Colloquy and would like to help support its development, please consider making a donation.

Requirements:
OS X 10.7-10.9
64-bit Intel