I'd probably say Leotek comes first. RUUD Lighting/BetaLED comes in second. There was a Leotek SL-36W1R-FX in my town that's probably been there before 2007 because it still shows up on the 2007 street view here.

Leotek even made LED streetlights as early as 2004!

This is as difficult to answer as to name the inventor of the electric lamp.  That title is usually given jointly to Joseph Swan and Thomas Edison, but in fact working electric lamps were made by dozens of other individuals many decades before them.  Edison & Swan only achieved fame because they were the first to produce a commercially viable electric lamp - one that was affordable, bright enough and with a long enough life to meet consumer requirements.

The same is true of LED streetlights.  There were experiments dating back to at least the 1970s but their light output was pathetic and the cost was huge.  It took another three decades before LED streetlights became both functional and affordable.

I believe the credit for the worlds’ first commercially viable LED streetlights goes to the Belgian company Schréder, which in 2007 made perhaps the first effective and large-scale installation at the city of Split in Croatia/Hrvatska.  Just prior to that in 2006, Cree demonstrated advanced prototypes of high power white LED streetlamps that had been made possible by the invention of their Xlamp 7090 emitters, but I don’t think those were sold.

Interesting, although I would have guessed that 20 tonne thing Kev has got from DW Windsor?, with its “slow ramp up diodes” controlled by circuitry like something off the star ship Enterprise! 

I don’t know, but the WRTL Stela was the first mainstream LED lantern to become popular in the UK.   

The same is true of LED streetlights.  There were experiments dating back to at least the 1970s but their light output was pathetic and the cost was huge.  It took another three decades before LED streetlights became both functional and affordable.

I believe the credit for the worlds’ first commercially viable LED streetlights goes to the Belgian company Schréder, which in 2007 made perhaps the first effective and large-scale installation at the city of Split in Croatia/Hrvatska.  Just prior to that in 2006, Cree demonstrated advanced prototypes of high power white LED streetlamps that had been made possible by the invention of their Xlamp 7090 emitters, but I don’t think those were sold.

I remember my uncle a Electronics Engineer was excited reading in 1998 +/- about a BLUE LED with high enough efficiency / power output to "drive" phosphor coatings leading the way to a "proper white" LED
I believe CREE had retail white LED "engines" available commercially around 2000
I would "expect" the early LED street lights to show up around 02 - 04 window and Leotek has bean pointed out as 2004