  We present a multiwavelength examination of the supernova remnant (SNR) S26
in the nearby galaxy NGC 300 using data from Chandra X-ray Observatory,
XMM-Newton X-ray Observatory, Hubble Space Telescope (HST), the Very Large
Array, and the Australia Telescope Compact Array. We simultaneously fit all of
the available X-ray data with a thermal plasma model and find a temperature of
$0.77 \pm 0.13$ keV with a hydrogen column density of
($9.7^{+6.4}_{-4.8}$)$\times 10^{20}$ cm$^{-2}$. HST imaging allows us to
measure a semimajor axis of $0.78 \pm 0.10$ arcsec ($7.5 \pm 1.0$ pc) and a
semiminor axis of $0.69^{+0.14}_{-0.12}$ arcsec ($6.7^{+1.2}_{-1.4}$ pc). This
precise size helps to constrain the age and velocity of the shock to be
($3.3^{+0.7}_{-0.6}$)$\times 10^{3}$ yr and $411^{+275}_{-122}$ km s$^{-1}$. We
also fit photometry of the surrounding stars to infer the age and mass of the
progenitor star to be $8 \pm 1$ Myr and $25^{+1}_{-5}$ M$_{\odot}$. Based on
measured radio properties of the source and assuming equipartition, the
estimated radio luminosity of $\sim 1.7 \times 10^{34}$ erg s$^{-1}$ over the
$10^{8}-10^{11}$ Hz frequency range results in a minimum magnetic field
associated with this SNR of $0.067$ mG and the minimum energy needed to power
the observed synchrotron emission of $1.5 \times 10^{49}$ erg. The size and
temperature of N300-S26 appear to be similar to the Galactic SNR G311.5-0.3
except that G311.5-0.3 has a significantly lower X-ray luminosity, is older,
and has a slower shock velocity.
