  For the Gegenbauer weight function $w_{\lambda}(t)=(1-t^2)^{\lambda-1/2}$,
$\lambda>-1/2$, we denote by $\Vert\cdot\Vert_{w_{\lambda}}$ the associated
$L_2$-norm, $$ \Vert
f\Vert_{w_{\lambda}}:=\Big(\int_{-1}^{1}w_{\lambda}(t)f^2(t)\,dt\Big)^{1/2}. $$
We study the Markov inequality $$ \Vert p^{\prime}\Vert_{w_{\lambda}}\leq
c_{n}(\lambda)\,\Vert p\Vert_{w_{\lambda}},\qquad p\in \mathcal{P}_n, $$ where
$\mathcal{P}_n$ is the class of algebraic polynomials of degree not exceeding
$n$. Upper and lower bounds for the best Markov constant $c_{n}(\lambda)$ are
obtained, which are valid for all $n\in \mathbb{N}$ and $\lambda>-\frac{1}{2}$.
