The aim of this paper is to define a chain level refinement of the Batalin-Vilkovisky (BV) algebra structure on the homology of the free loop space of a closed, oriented C ∞ -manifold. For this purpose, we define a (nonsymmetric) cyclic dg operad which consists of "de Rham chains" of free loops with marked points. A notion of de Rham chains, which is a certain hybrid of the notions of singular chains and differential forms, is a key ingredient in our construction. Combined with a generalization of cyclic Deligne's conjecture, this dg operad produces a chain model of the free loop space which admits an action of a chain model of the framed little disks operad, recovering the string topology BV algebra structure on the homology level.2010 Mathematics Subject Classification. 55P50, 57N75, 18D50. 1 well-known fact: the cup product on (singular) cohomology can be defined at the chain level, and (part of) extra information is used to define the classical Massey products; see [22] Section 9.4.5. For (a), what is called Deligne's conjecture claims that a certain chain model of the little disks operad acts on the Hochschild cochain complex. Various affirmative solutions to this conjecture and its variations are known; see [23] Part I Section 1.19, [22] Section 13.3.15, and the references therein. The aim of this paper is to propose a chain level algebraic structure which lifts (b) (the Batalin-Vilkovisky (BV) algebra structure in string topology), and compare it with a solution to Deligne's conjecture via a chain map which is a chain level lift of (c).Our construction is based on generalizations of Deligne's conjecture in operadic contexts. More specifically, we use results in a recent paper [28], which we describe here very briefly. For any (nonsymmetric) dg operad O = (O(k)) k≥0 and a Maurer-Cartan element ζ = (ζ k ) k≥2 of O, one can assign a chain complex (Õ, ∂ ζ ) (here we use our notation in Section 2.5, which is different from the notation in [28]). Then Theorem A in [28] asserts that the chain complexÕ admits an action of a certain chain model of the little disks operad. Moreover, if O has a unital cyclic structure and ζ is cyclically invariant, Theorem B in [28] asserts that this action extends to an action of a certain chain model of the framed little disks operad (strictly speaking, in Theorem B one has to consider a quasi-isomorphic subcomplexÕ nm ⊂Õ which consists of "normalized chains"). Actually, in this paper we consider only the simple case that ζ k = 0 for every k = 2. A Maurer-Cartan element satisfying this condition is equivalent to a "multiplication" of the operad (see Definition 2.6). Let us briefly describe our main result. For any closed oriented C ∞ -manifold M , we define a nonsymmetric cyclic dg operad O M with a multiplication and a unit. Applying Theorem B in [28], the associated chain complex O M nm admits an action of a chain model of the framed little disks operad. In particular, the homology H * ( O M nm ) ∼ = H * ( O M ) has a BV algebra structure. Then we show that there exists an isomor...