The Sphere Builders are aliens from another dimension in the fictional Star Trek universe. They are bent on conquering the galaxy by reconfiguring the fabric of space to make it more hospitible to them using specially designed moon-sized spheres. They were first seen in the 2004 Star Trek: Enterprise episode "Harbinger".

By approximately the year 2550 , the Sphere Builders were on the verge of accomplishing their goal when they created a habitable sphere about 50,000 light years in all directions. However, as Daniels showed Jonathan Archer on board the Enterprise-J, the United Federation of Planets engaged the Sphere Builders at the Battle of Procyon Five and ultimately pushed them back to their trans-dimensional realm, preventing a galactic holocaust.

The Sphere Builders have the technology to examine multiple timelines. Since they saw the future with the Federation, the Sphere Builders tried to change history in their favor by informing the Xindi in 2152 that humanity would ultimately destroy them, so as to panic them into attacking and ultimately destroying Earth.

When Archer tried to tell the Xindi Council that the Sphere Builders were the enemy, Degra told him that the Council may not believe him. After Xindus, the Xindi homeworld, was destroyed, the Sphere Builders helped guide the five species toward habitable planets and precious resources. The Xindi then called them the "Guardians". Like the Triannons, the Xindi referred to the "Guardians" with reverence. Degra was taught and taught his children to thank the "Guardians" at the end of each day for helping them.

Sphere 41

Sphere 41 was the "Control Sphere" for the network of spheres built by the trans-dimensional Sphere Builders in the Delphic Expanse. It was destroyed in the episode "Zero Hour." This resulted in the entire network of spheres collapsing via a chain reaction and the spatial anomalies that they had created disappearing.

Connections to Other Races

The physical appearance and costuming of the Sphere Builders, and the outer appearance of their spheres are thought by some fans to be similar to that of the Borg. This connection may be contrived, because the Sphere Builders have no cybernetic implants and operate as individuals. Their appearance has more in common with the first humanoids to inhabit the galaxy, or even the Founders of the Dominion. Both the Builders and the Borg have the technology to explore other dimensions, but the same could be said for the Federation.