With a suitable decomposition of its energymomentum tensor into pressureless matter and a vacuum type term, we investigate the spherical gravitational collapse of a minimally coupled, self-interacting scalar field, showing that it collapses to a singularity. The formed blackhole has a mass M ∼ 1/m (in Planck units), where m is the mass of the scalar field. If the latter has the axion mass, m ∼ 10 −5 eV, the former has a mass M ∼ 10 −5 M .The interface between cosmology and blackhole physics has been always fertile, leading to theoretical insights and mathematical analogies that go from singularity theorems to Hawking radiation and holography [1][2][3][4][5]. This interface is a counterpart of another rich interplay between processes occurring in the primordial universe and those characteristic of dense nuclear media like relativistic stars. In the cosmological realm, a relatively recent approach to the dark sector has been based on unified descriptions where both the dark energy and the dark matter are described by a single fluid, formed for example by a generalised Chaplygin gas [6][7][8][9][10][11][12], or by a non-adiabatic scalar field [13][14][15][16][17]. In this context, it is natural to ask whether such unified fluids can also allow for star-like and blackhole solutions [18,19]. Scalar field blackholes have been investigated in de Sitter and anti-de Sitter backgrounds, in both conformal and massive cases [20,21]. Blackhole and wormhole solutions have been found with phantom fields as well [22]. From an astrophysical viewpoint, these solutions are particularly interesting in the case of an axion field [23,24], the only stable scalar predicted by the standard model of particles, and one of the natural candidates for the unobserved dark matter particle. Axionic blackholes are also interesting because of the possible signature the accretion of axions can leave on future gravitational waves S. Carneiro: In sabbatical from Instituto de Física, Universidade Federal da Bahia, 40210-340, Salvador, Bahia, Brazil. a e-mail: saulo.carneiro.ufba@gmail.com observations [25]. Accretion of scalar fields into blackholes was studied, for example, in [26].A minimally coupled scalar field has energy-momentum tensorwhere V (φ) is the self-interaction potential. We can formally decompose it into pressureless and "vacuum" componentsThe "matter" density is defined as ρ = T μ mμ , and the scalar field 4-velocity byThe vacuum density ρ = is a covariant scalar, and its equation of state, p = −ρ , is the same for any observer. Using the above decomposition, it was shown elsewhere that a scalar field can accomplish for both dark components observed in the cosmic fluid [16,17]. The component does not cluster at linear order and is responsible for the expansion acceleration. The pressureless one, on the other hand, can be identified with observed clustering matter. With an appropriate choice of the scalar field potential, we have the same phenomenology of non-adiabatic generalised Chaplygin gases, which includes the standard ...