  Recent high-resolution X-ray spectroscopy revealed possible presence of
charge exchange (CX) X-ray emission in supernova remnants (SNRs). Although CX
is expected to take place at outermost edges of SNR shells, no significant
measurement has been reported so far due to the lack of nearby SNR samples.
Here we present an X-ray study of SNR G296.1$-$0.5, which has a complicated
multiple-shell structure, with the Reflection Grating Spectrometer (RGS)
onboard XMM-Newton. We select two shells in different regions and find that in
both regions O VII line shows a high forbidden-to-resonance ($f/r$) ratio that
cannot be reproduced by a simple thermal model. Our spectral analysis suggests
a presence of CX and the result is also supported by our new radio observation,
where we discover evidence of molecular clouds associated with these shells.
Assuming G296.1$-$0.5 has a spherical shock, we estimate that CX is dominant in
a thin layer with a thickness of 0.2--0.3\% of the shock radius. The result is
consistent with a previous theoretical expectation and we therefore conclude
that CX occurs in G296.1$-$0.5.
