Wis. Stat. § 701.0204: Venue.

(1) Except as provided in sub. (2), venue for a judicial proceeding involving a trust may be in the county of this state in which the trust’s principal place of administration is or will be located or, if the trust is a testamentary trust and the decedent’s estate is not yet closed, in the county of this state in which the decedent’s estate is being administered.

(2) If a trust has no trustee, venue for a judicial proceeding for the appointment of a trustee is in any of the following:

(a) A county of this state in which a beneficiary resides.

(b) A county of this state in which any trust property is located.

(c) A county of this state in which the holder of trust property maintains an office.

(d) If the trust is a testamentary trust and the decedent’s estate is not yet closed, in the county of this state in which the decedent’s estate is being administered.

(3) Venue for a judicial proceeding involving a trust is also governed by ss. 801.50 to 801.62, as applicable, and the proceeding is regarded as a civil action for that purpose.