if in-case you use Dockerfile & Linux

RUN wget "https://storage.googleapis.com/kubernetes-helm/helm-$(wget -qO- https://github.com/kubernetes/helm/releases | sed -n '/Latest release<\/a>/,$p' | grep -oE 'v[0-9]+\.[0-9]+\.[0-9]+' |head -1)-linux-amd64.tar.gz"

For Linux, OSX, and Windows targets:

HELM_INSTALL_DIR=[‘desired path’]
USE_SUDO=[‘true’|’false’]
curl https://raw.githubusercontent.com/helm/helm/master/scripts/get-helm-3 | bash

Other install options: Helm Install Documentation

Recommend migration away from V2.x as soon as you can.

And, for those without wget:

HVER=$(curl -sSL https://github.com/kubernetes/helm/releases | sed -n '/Latest release<\/a>/,$p' | grep -oE 'v[0-9]+\.[0-9]+\.[0-9]+' | head -1)

echo $HVER

Result (currently):

v2.9.1

To download the gz that contains the latest Helm executable:

Linux

curl -LO https://storage.googleapis.com/kubernetes-helm/helm-${HVER}-linux-amd64.tar.gz

OSX

curl -LO https://storage.googleapis.com/kubernetes-helm/helm-${HVER}-darwin-amd64.tar.gz

Windows (bash ell)

curl -LO https://storage.googleapis.com/kubernetes-helm/helm-${HVER}-windows-amd64.tar.gz