We propose that the energetic major outburst of the supernova (SN) impostor SN 2009ip in 2012 September (outburst 2012b) was a mergerburst event, where two massive stars merged. The previous outbursts of 2009 and 2011 might have occurred near periastron passages of the binary system prior to the merger, in a similar manner to the luminosity peaks in the 19th century Great Eruption of the massive binary system Eta Carinae. The major 2012b outburst and the 2012a pre-outburst resemble the light curve of the mergerburst event V838 Mon. A merger of an evolved star with a mass of M1 ∼ 60-100 M ⊙ and a secondary main-sequence star of M2 ∼ 0.2-0.5 M1 can account for the energy of SN 2009ip and for the high velocities of the ejected gas. The ejected nebula is expected to have a non-spherical structure, e.g., bipolar or even a more complicated morphology.