It is now about 30 years ago that photometric and spectroscopic surveys of asymptotic giant branch (AGB) stars in the Magellanic Clouds (MCs) uncovered the first examples of truly massive (> 3-4 M_ȯ) O-rich AGB stars experiencing hot bottom burning (HBB). Massive (Li-rich) HBB AGB stars were later identified in our own Galaxy and they pertain to the Galactic population of obscured OH/IR stars. High-resolution optical spectroscopic surveys have revealed the massive Galactic AGB stars to be strongly enriched in Rb compared to other nearby s-process elements like Zr, confirming that Ne22 is the dominant neutron source in these stars. Similar surveys of OH/IR stars in the MCs disclosed their Rb-rich low-metallicity counterparts, showing that these stars are usually brighter (because of HBB flux excess) than the standard adopted luminosity limit for AGB stars (Mbol ˜ -7.1) and that they might have stellar masses of at least ˜6-7 M_ȯ. The chemical composition and photometric variability are efficient in separating the massive AGB stars from massive red supergiants (RSG) but the main difficulty is to distinguish between massive AGB and super-AGB stars because the present theoretical nucleosynthesis models predict both stars to be chemically identical. Here I review the available multiwavelength (from the optical to the far-IR) observations on massive AGB and super-AGB stars as well as the current caveats and limitations in our undestanding of these stars. Finally, I underline the expected observations on massive AGB and super-AGB stars from on-going massive surveys like Gaia and SDSS-IV/APOGEE-2 and future facilities such as the James Webb Space Telescope.