Kool & Elfring is a Dutch boutique amplifier company founded in 2007 by Aryjan Kool and Floris Elfring. Based in the Netherlands roughly 35–45 kilometers from Amsterdam, the company began by hand-building guitar and bass speaker cabinets before releasing its first head, the Black Rose, named after the Thin Lizzy album. The brand built a reputation in European boutique circles for hand-wired, point-to-point tube amplifiers with no PCB construction.

The lineup expanded with the Ace, a single-channel head voiced around the '59 Bassmann and '62 JTM45, and the Super 7. Other models include The 11, an EL34-powered single-channel amp built around a vintage Plexi voicing, along with the Marvell and 1984 multi-channel heads, the Blue Sky pedalboard platform, matching 1x12 and 2x12 cabinets, and the all-tube Ace Boost pedal designed to push a tube amp's front end.

In 2015 Floris Elfring left the partnership to start his own company, Elfring Amps and More, while Aryjan Kool continued the original operation under the name Kool Amplification. Used Kool & Elfring–branded heads, combos, cabinets, and pedals from the 2007–2015 era still circulate on the European boutique market through dealers such as Banzai Music and on Reverb.

Kool & Elfring has 5 products cataloged on Equipboard, including Guitar Amplifier Cabinets, Guitar Amplifier Heads, and Boost Effects Pedals. Their gear is featured by 1 artist, with the strongest followings in Rock, Pop, and Folk, World, & Country. Notable users include J.B. Meijers.