  We report extensive differential V-band photometry and high-resolution
spectroscopic observations of the early F-type, 1.06-day detached eclipsing
binary V506 Oph. The observations along with times of minimum light from the
literature are used to derive a very precise ephemeris and the physical
properties for the components, with the absolute masses and radii being
determined to 0.7% or better. The masses are 1.4153 +/- 0.0100 M(Sun) and
1.4023 +/- 0.0094 M(sun) for the primary and secondary, the radii are 1.725 +/-
0.010 R(Sun) and 1.692 +/- 0.012 R(Sun), and the effective temperatures 6840
+/- 150 K and 6780 +/- 110 K, respectively. The orbit is circular and the stars
are rotating synchronously. The accuracy of the radii and temperatures is
supported by the resulting distance estimate of 564 +/- 30 pc, in excellent
agreement with the value implied by the trigonometric parallax listed in the
Gaia/DR2 catalog. Current stellar evolution models from the MIST series for a
composition of [Fe/H] = -0.04 match the properties of both stars in V506 Oph
very well at an age of 1.83 Gyr, and indicate they are halfway through their
core hydrogen-burning phase.
