Strain engineering is ubiquitous in design and fabrication of innovative, high-performance electronic, optoelectronic, and photovoltaic devices. Raman spectroscopy is one of the most straightforward techniques that has been utilized to estimate the localized strain. However, this technique is incapable of measuring the individual components of stress and the only information that it can provide is reduced to the average in-plane strain from (001) surface. Herein, we circumvent this major limitation by employing high numerical aperture oil-immersed objective lens combined with optimized light polarization conditions. We demonstrate the application of Raman spectroscopy to simultaneously probe the two local stress in-plane components in individual ultrathin strained silicon nanowires with diameters in the 30-80 nm range. This ability to measure locally the stress components in a single nanowire creates valuable opportunities for a straightforward and precise mapping of stress in a variety of emerging strain-engineered nanoscale materials and devices.